reproducible debian: build.sh: apply the 120m timeout directly to diffoscope...

reproducible debian: build.sh: apply the 120m timeout directly to diffoscope instead of the wrapping schroot

We are seeing schroot errors like the following, that I believe would be
fixed by SIGTERMing diffoscope directly instead of schroot → sh →
diffoscope.

+ local TIMEOUT=120m
+ DBDSUITE=unstable
+ '[' unstable = experimental ']'
+ set -x
++ mktemp --tmpdir=/srv/reproducible-results/rbuild-debian/tmp.OQJmsWHPbc -d dbd-tmp-XXXXXXX
+ local TEMP=/srv/reproducible-results/rbuild-debian/tmp.OQJmsWHPbc/dbd-tmp-aiOGwgn
++ schroot --begin-session -c chroot:jenkins-reproducible-unstable-diffoscope
+ local session=jenkins-reproducible-unstable-diffoscope-ebd86728-8ca4-4419-8c00-e9b25b6f286f
++ schroot --directory /srv/reproducible-results/rbuild-debian/tmp.OQJmsWHPbc --run-session -c jenkins-reproducible-unstable-diffoscope-ebd86728-8ca4-4419-8c00-e9b25b6f286f diffoscope -- --version
+ DIFFOSCOPE='diffoscope 96'
+ log_info 'diffoscope 96 will be used to compare the two builds:'
+ _log I: 'diffoscope 96 will be used to compare the two builds:'
+ local prefix=I:
+ shift 1
+ tee -a /var/lib/jenkins/userContent/reproducible/debian/rbuild/unstable/arm64/gcc-5_5.5.0-12.rbuild.log
++ date -u
+ echo -e 'Wed Jun 20 09:34:15 UTC 2018  I: diffoscope 96 will be used to compare the two builds:'
Wed Jun 20 09:34:15 UTC 2018  I: diffoscope 96 will be used to compare the two builds:
+ set +e
+ set -x
+ timeout 120m nice schroot --directory /srv/reproducible-results/rbuild-debian/tmp.OQJmsWHPbc --run-session -c jenkins-reproducible-unstable-diffoscope-ebd86728-8ca4-4419-8c00-e9b25b6f286f -- sh -c 'export TMPDIR=/srv/reproducible-results/rbuild-debian/tmp.OQJmsWHPbc/dbd-tmp-aiOGwgn ; diffoscope 			--html /srv/reproducible-results/rbuild-debian/tmp.OQJmsWHPbc/gcc-5_5.5.0-12.diffoscope.html 			--text /srv/reproducible-results/rbuild-debian/tmp.OQJmsWHPbc/gcc-5_5.5.0-12.diffoscope.txt 			--profile=- 			/srv/reproducible-results/rbuild-debian/tmp.OQJmsWHPbc/b1/gcc-5_5.5.0-12_arm64.changes 			/srv/reproducible-results/rbuild-debian/tmp.OQJmsWHPbc/b2/gcc-5_5.5.0-12_arm64.changes'
+ RESULT=124
+ false
+ set +x
E: Caught signal ‘Terminated’: terminating immediately
E: Caught signal ‘Terminated’
E: 10mount: umount: /run/schroot/mount/jenkins-reproducible-unstable-diffoscope-ebd86728-8ca4-4419-8c00-e9b25b6f286f/srv/reproducible-results: target is busy
E: 10mount:         (In some cases useful info about processes that
E: 10mount:          use the device is found by lsof(8) or fuser(1).)
E: 10mount: umount: /run/schroot/mount/jenkins-reproducible-unstable-diffoscope-ebd86728-8ca4-4419-8c00-e9b25b6f286f: target is busy
E: 10mount:         (In some cases useful info about processes that
E: 10mount:          use the device is found by lsof(8) or fuser(1).)
E: 10mount: rmdir: failed to remove '/var/run/schroot/mount/jenkins-reproducible-unstable-diffoscope-ebd86728-8ca4-4419-8c00-e9b25b6f286f': Device or resource busy
E: jenkins-reproducible-unstable-diffoscope-ebd86728-8ca4-4419-8c00-e9b25b6f286f: Chroot setup failed: stage=setup-stop
Starting cleanup.

Signed-off-by: Mattia Rizzolo <mattia@debian.org>