travis-ci: use 'set -e' in the 32 bit Linux build job

The script 'ci/run-linux32-build.sh' running inside the Docker container of the 32 bit Linux build job uses an && chain to break the build if one of the commands fails. This is problematic for two reasons: - The && chain is broken, because there is this in the middle: test -z $HOST_UID || (CI_USER="ci" && useradd -u $HOST_UID $CI_USER) && Luckily it is broken in a way that it didn't lead to false successes. If installing dependencies fails, then the rest of the first && chain is skipped and execution resumes after the || operator. At that point $HOST_UID is still unset, causing 'useradd' to error out with "invalid user ID 'ci'", which in turn causes the second && chain to abort the script and thus break the build. - All other 'ci/*' scripts use 'set -e' to break the build if one of the commands fails. This inconsistency among these scripts is asking for trouble: I forgot about the && chain more than once while working on this patch series. Enable 'set -e' for the whole script and for the commands executed under 'su' as well. While touching every line in the 'su' command block anyway, change their indentation to use a tab instead of spaces. Signed-off-by: SZEDER Gábor <szeder.dev@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>