Disable colored output in shellcheck

shellcheck defaults to using colors in its output.  Unfortunately,
jenkins is unable to process bash-style colors in the console log, so in
practice, when colors are used, the jenkins logs end up like:

[1mIn jenkins/userid-validation line 25:[0m
[0mif [ "x${COMMITTER_EMAIL}" == "x" ]; then[0m
[32m     ^-------------------^ SC2268 (style): Avoid x-prefix in comparisons as it no longer serves a purpose.[0m

[1mDid you mean: [0m
if [ "${COMMITTER_EMAIL}" == "" ]; then

With lots of control characters.  This is annoying to review in build
scripts, which are primarily being read from disk somewhere.

The above log was pulled from the review here:
https://jenkins.openbmc.org/job/CI-MISC/job/ci-openbmc-build-scripts/455/console

Signed-off-by: Ed Tanous <edtanous@google.com>
Change-Id: Ibc827039150f7018b31a63ac11fa7c19776414c9
1 file changed