Diff of the two buildlogs:

--
--- b1/build.log	2024-07-07 09:18:50.327076561 +0000
+++ b2/build.log	2024-07-07 09:52:04.242466544 +0000
@@ -1,6 +1,6 @@
 I: pbuilder: network access will be disabled during build
-I: Current time: Sat Jul  6 21:00:11 -12 2024
-I: pbuilder-time-stamp: 1720342811
+I: Current time: Sun Jul  7 23:19:09 +14 2024
+I: pbuilder-time-stamp: 1720343949
 I: Building the build Environment
 I: extracting base tarball [/var/cache/pbuilder/unstable-reproducible-base.tgz]
 I: copying local configuration
@@ -26,52 +26,84 @@
 dpkg-source: info: unpacking coq-bignums_9.0.0+coq8.20-1.debian.tar.xz
 I: Not using root during the build.
 I: Installing the build-deps
-I: user script /srv/workspace/pbuilder/30231/tmp/hooks/D02_print_environment starting
+I: user script /srv/workspace/pbuilder/3020/tmp/hooks/D01_modify_environment starting
+debug: Running on ff64a.
+I: Changing host+domainname to test build reproducibility
+I: Adding a custom variable just for the fun of it...
+I: Changing /bin/sh to bash
+'/bin/sh' -> '/bin/bash'
+lrwxrwxrwx 1 root root 9 Jul  7 09:20 /bin/sh -> /bin/bash
+I: Setting pbuilder2's login shell to /bin/bash
+I: Setting pbuilder2's GECOS to second user,second room,second work-phone,second home-phone,second other
+I: user script /srv/workspace/pbuilder/3020/tmp/hooks/D01_modify_environment finished
+I: user script /srv/workspace/pbuilder/3020/tmp/hooks/D02_print_environment starting
 I: set
-  BUILDDIR='/build/reproducible-path'
-  BUILDUSERGECOS='first user,first room,first work-phone,first home-phone,first other'
-  BUILDUSERNAME='pbuilder1'
-  BUILD_ARCH='armhf'
-  DEBIAN_FRONTEND='noninteractive'
-  DEB_BUILD_OPTIONS='buildinfo=+all reproducible=+all parallel=3 '
-  DISTRIBUTION='unstable'
-  HOME='/root'
-  HOST_ARCH='armhf'
+  BASH=/bin/sh
+  BASHOPTS=checkwinsize:cmdhist:complete_fullquote:extquote:force_fignore:globasciiranges:globskipdots:hostcomplete:interactive_comments:patsub_replacement:progcomp:promptvars:sourcepath
+  BASH_ALIASES=()
+  BASH_ARGC=()
+  BASH_ARGV=()
+  BASH_CMDS=()
+  BASH_LINENO=([0]="12" [1]="0")
+  BASH_LOADABLES_PATH=/usr/local/lib/bash:/usr/lib/bash:/opt/local/lib/bash:/usr/pkg/lib/bash:/opt/pkg/lib/bash:.
+  BASH_SOURCE=([0]="/tmp/hooks/D02_print_environment" [1]="/tmp/hooks/D02_print_environment")
+  BASH_VERSINFO=([0]="5" [1]="2" [2]="21" [3]="1" [4]="release" [5]="arm-unknown-linux-gnueabihf")
+  BASH_VERSION='5.2.21(1)-release'
+  BUILDDIR=/build/reproducible-path
+  BUILDUSERGECOS='second user,second room,second work-phone,second home-phone,second other'
+  BUILDUSERNAME=pbuilder2
+  BUILD_ARCH=armhf
+  DEBIAN_FRONTEND=noninteractive
+  DEB_BUILD_OPTIONS='buildinfo=+all reproducible=+all parallel=6 '
+  DIRSTACK=()
+  DISTRIBUTION=unstable
+  EUID=0
+  FUNCNAME=([0]="Echo" [1]="main")
+  GROUPS=()
+  HOME=/root
+  HOSTNAME=i-capture-the-hostname
+  HOSTTYPE=arm
+  HOST_ARCH=armhf
   IFS=' 	
   '
-  INVOCATION_ID='410f3b945896441395bbe7db6f482411'
-  LANG='C'
-  LANGUAGE='en_US:en'
-  LC_ALL='C'
-  MAIL='/var/mail/root'
-  OPTIND='1'
-  PATH='/usr/sbin:/usr/bin:/sbin:/bin:/usr/games'
-  PBCURRENTCOMMANDLINEOPERATION='build'
-  PBUILDER_OPERATION='build'
-  PBUILDER_PKGDATADIR='/usr/share/pbuilder'
-  PBUILDER_PKGLIBDIR='/usr/lib/pbuilder'
-  PBUILDER_SYSCONFDIR='/etc'
-  PPID='30231'
-  PS1='# '
-  PS2='> '
+  INVOCATION_ID=db465017957c4f618a80c5ebe54fe5d4
+  LANG=C
+  LANGUAGE=it_CH:it
+  LC_ALL=C
+  MACHTYPE=arm-unknown-linux-gnueabihf
+  MAIL=/var/mail/root
+  OPTERR=1
+  OPTIND=1
+  OSTYPE=linux-gnueabihf
+  PATH=/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/i/capture/the/path
+  PBCURRENTCOMMANDLINEOPERATION=build
+  PBUILDER_OPERATION=build
+  PBUILDER_PKGDATADIR=/usr/share/pbuilder
+  PBUILDER_PKGLIBDIR=/usr/lib/pbuilder
+  PBUILDER_SYSCONFDIR=/etc
+  PIPESTATUS=([0]="0")
+  POSIXLY_CORRECT=y
+  PPID=3020
   PS4='+ '
-  PWD='/'
-  SHELL='/bin/bash'
-  SHLVL='2'
-  SUDO_COMMAND='/usr/bin/timeout -k 18.1h 18h /usr/bin/ionice -c 3 /usr/bin/nice /usr/sbin/pbuilder --build --configfile /srv/reproducible-results/rbuild-debian/r-b-build.hIrpRwCv/pbuilderrc_eT9i --distribution unstable --hookdir /etc/pbuilder/first-build-hooks --debbuildopts -b --basetgz /var/cache/pbuilder/unstable-reproducible-base.tgz --buildresult /srv/reproducible-results/rbuild-debian/r-b-build.hIrpRwCv/b1 --logfile b1/build.log coq-bignums_9.0.0+coq8.20-1.dsc'
-  SUDO_GID='116'
-  SUDO_UID='112'
-  SUDO_USER='jenkins'
-  TERM='unknown'
-  TZ='/usr/share/zoneinfo/Etc/GMT+12'
-  USER='root'
-  _='/usr/bin/systemd-run'
-  http_proxy='http://10.0.0.15:3142/'
+  PWD=/
+  SHELL=/bin/bash
+  SHELLOPTS=braceexpand:errexit:hashall:interactive-comments:posix
+  SHLVL=3
+  SUDO_COMMAND='/usr/bin/timeout -k 24.1h 24h /usr/bin/ionice -c 3 /usr/bin/nice -n 11 /usr/bin/unshare --uts -- /usr/sbin/pbuilder --build --configfile /srv/reproducible-results/rbuild-debian/r-b-build.hIrpRwCv/pbuilderrc_U4dd --distribution unstable --hookdir /etc/pbuilder/rebuild-hooks --debbuildopts -b --basetgz /var/cache/pbuilder/unstable-reproducible-base.tgz --buildresult /srv/reproducible-results/rbuild-debian/r-b-build.hIrpRwCv/b2 --logfile b2/build.log coq-bignums_9.0.0+coq8.20-1.dsc'
+  SUDO_GID=114
+  SUDO_UID=109
+  SUDO_USER=jenkins
+  TERM=unknown
+  TZ=/usr/share/zoneinfo/Etc/GMT-14
+  UID=0
+  USER=root
+  _='I: set'
+  http_proxy=http://10.0.0.15:3142/
 I: uname -a
-  Linux cbxi4b 6.1.0-22-armmp #1 SMP Debian 6.1.94-1 (2024-06-21) armv7l GNU/Linux
+  Linux i-capture-the-hostname 6.1.0-22-arm64 #1 SMP Debian 6.1.94-1 (2024-06-21) aarch64 GNU/Linux
 I: ls -l /bin
   lrwxrwxrwx 1 root root 7 Jun  5 22:35 /bin -> usr/bin
-I: user script /srv/workspace/pbuilder/30231/tmp/hooks/D02_print_environment finished
+I: user script /srv/workspace/pbuilder/3020/tmp/hooks/D02_print_environment finished
  -> Attempting to satisfy build-dependencies
  -> Creating pbuilder-satisfydepends-dummy package
 Package: pbuilder-satisfydepends-dummy
@@ -181,7 +213,7 @@
 Get: 62 http://deb.debian.org/debian unstable/main armhf libgmp3-dev armhf 2:6.3.0+dfsg-2+b1 [322 kB]
 Get: 63 http://deb.debian.org/debian unstable/main armhf libzarith-ocaml-dev armhf 1.13-2+b1 [101 kB]
 Get: 64 http://deb.debian.org/debian unstable/main armhf libcoq-core-ocaml-dev armhf 8.19.1+dfsg-2 [46.0 MB]
-Fetched 312 MB in 45s (6951 kB/s)
+Fetched 312 MB in 42s (7480 kB/s)
 debconf: delaying package configuration, since apt-utils is not installed
 Selecting previously unselected package libpython3.12-minimal:armhf.
 (Reading database ... 
(Reading database ... 5%
(Reading database ... 10%
(Reading database ... 15%
(Reading database ... 20%
(Reading database ... 25%
(Reading database ... 30%
(Reading database ... 35%
(Reading database ... 40%
(Reading database ... 45%
(Reading database ... 50%
(Reading database ... 55%
(Reading database ... 60%
(Reading database ... 65%
(Reading database ... 70%
(Reading database ... 75%
(Reading database ... 80%
(Reading database ... 85%
(Reading database ... 90%
(Reading database ... 95%
(Reading database ... 100%
(Reading database ... 19413 files and directories currently installed.)
@@ -403,8 +435,8 @@
 Setting up tzdata (2024a-4) ...
 
 Current default time zone: 'Etc/UTC'
-Local time is now:      Sun Jul  7 09:05:03 UTC 2024.
-Universal Time is now:  Sun Jul  7 09:05:03 UTC 2024.
+Local time is now:      Sun Jul  7 09:29:12 UTC 2024.
+Universal Time is now:  Sun Jul  7 09:29:12 UTC 2024.
 Run 'dpkg-reconfigure tzdata' if you wish to change it.
 
 Setting up autotools-dev (20220109.1) ...
@@ -464,7 +496,11 @@
 Building tag database...
  -> Finished parsing the build-deps
 I: Building the package
-I: Running cd /build/reproducible-path/coq-bignums-9.0.0+coq8.20/ && env PATH="/usr/sbin:/usr/bin:/sbin:/bin:/usr/games" HOME="/nonexistent/first-build" dpkg-buildpackage -us -uc -b && env PATH="/usr/sbin:/usr/bin:/sbin:/bin:/usr/games" HOME="/nonexistent/first-build" dpkg-genchanges -S  > ../coq-bignums_9.0.0+coq8.20-1_source.changes
+I: user script /srv/workspace/pbuilder/3020/tmp/hooks/A99_set_merged_usr starting
+Not re-configuring usrmerge for unstable
+I: user script /srv/workspace/pbuilder/3020/tmp/hooks/A99_set_merged_usr finished
+hostname: Name or service not known
+I: Running cd /build/reproducible-path/coq-bignums-9.0.0+coq8.20/ && env PATH="/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/i/capture/the/path" HOME="/nonexistent/second-build" dpkg-buildpackage -us -uc -b && env PATH="/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/i/capture/the/path" HOME="/nonexistent/second-build" dpkg-genchanges -S  > ../coq-bignums_9.0.0+coq8.20-1_source.changes
 dpkg-buildpackage: info: source package coq-bignums
 dpkg-buildpackage: info: source version 9.0.0+coq8.20-1
 dpkg-buildpackage: info: source distribution unstable
@@ -505,7 +541,7 @@
    dh_ocamlinit
    dh_auto_configure
    dh_auto_build
-	make -j3 "INSTALL=install --strip-program=true"
+	make -j6 "INSTALL=install --strip-program=true"
 make[1]: Entering directory '/build/reproducible-path/coq-bignums-9.0.0+coq8.20'
 coq_makefile -f _CoqProject -o Makefile.coq
 make -f Makefile.coq Makefile
@@ -533,10 +569,11 @@
 COQC CyclicDouble/DoubleDivn1.v
 COQC SpecViaZ/NSig.v
 COQC SpecViaZ/ZSig.v
-COQC CyclicDouble/DoubleDiv.v
 COQC SpecViaZ/NSigNAxioms.v
 COQC SpecViaZ/ZSigZAxioms.v
 COQC BigQ/QMake.v
+COQC BigZ/ZMake.v
+COQC CyclicDouble/DoubleDiv.v
 File "./CyclicDouble/DoubleDiv.v", line 1143, characters 28-46:
 Warning: Notation Zis_gcd_for_euclid is deprecated since 8.17.
 [deprecated-syntactic-definition-since-8.17,deprecated-since-8.17,deprecated-syntactic-definition,deprecated,default]
@@ -549,7 +586,6 @@
 File "./CyclicDouble/DoubleDiv.v", line 1493, characters 9-27:
 Warning: Notation Zis_gcd_for_euclid is deprecated since 8.17.
 [deprecated-syntactic-definition-since-8.17,deprecated-since-8.17,deprecated-syntactic-definition,deprecated,default]
-COQC BigZ/ZMake.v
 COQC CyclicDouble/DoubleCyclic.v
 COQC BigN/Nbasic.v
 COQC BigN/NMake_gen.v
@@ -584,7 +620,7 @@
    create-stamp debian/debhelper-build-stamp
    dh_prep
    dh_auto_install --destdir=debian/libcoq-bignums/
-	make -j3 install DESTDIR=/build/reproducible-path/coq-bignums-9.0.0\+coq8.20/debian/libcoq-bignums AM_UPDATE_INFO_DIR=no "INSTALL=install --strip-program=true"
+	make -j6 install DESTDIR=/build/reproducible-path/coq-bignums-9.0.0\+coq8.20/debian/libcoq-bignums AM_UPDATE_INFO_DIR=no "INSTALL=install --strip-program=true"
 make[1]: Entering directory '/build/reproducible-path/coq-bignums-9.0.0+coq8.20'
 make -f Makefile.coq Makefile
 make[2]: Entering directory '/build/reproducible-path/coq-bignums-9.0.0+coq8.20'
@@ -712,12 +748,14 @@
 dpkg-buildpackage: info: binary-only upload (no source included)
 dpkg-genchanges: info: including full source code in upload
 I: copying local configuration
+I: user script /srv/workspace/pbuilder/3020/tmp/hooks/B01_cleanup starting
+I: user script /srv/workspace/pbuilder/3020/tmp/hooks/B01_cleanup finished
 I: unmounting dev/ptmx filesystem
 I: unmounting dev/pts filesystem
 I: unmounting dev/shm filesystem
 I: unmounting proc filesystem
 I: unmounting sys filesystem
 I: cleaning the build env 
-I: removing directory /srv/workspace/pbuilder/30231 and its subdirectories
-I: Current time: Sat Jul  6 21:18:45 -12 2024
-I: pbuilder-time-stamp: 1720343925
+I: removing directory /srv/workspace/pbuilder/3020 and its subdirectories
+I: Current time: Sun Jul  7 23:51:57 +14 2024
+I: pbuilder-time-stamp: 1720345917