[Packaging] Change exit code when skipping build of i386
[Packaging] Change exit code when skipping build of i386

When skipping unnecessary build of i386 because of architecture 'all'
we now return exit code 50. This allows the caller to detect this
condition and report this build ask 'skipped'.

Change-Id: I0821c3b8d94854f90620ec1274ad18aea0d15b90

sillsdev/ci-builder-scripts,sillsdev/ci-builder-scripts,sillsdev/ci-builder-scripts