Previously, only Windows had the plumbing to rename test results for
the Kokoro result viewers to pretty-print.
macos.cfg was the only CI that lacked a corresponding .sh, which maked
unix.sh harder to reason about. Created macos.sh so that unix.sh is now
just a helper script and will not be called directly by Kokoro.
We now avoid "gradle clean" to avoid wiping results. Still clean compiler
since we do re-run the build multiple times with varying platforms.
Shouldn't be necessary, but "just in case" since I want this commit to
be low risk. This improves Windows to produce detailed results even
if the CI was successful.
Eric Anderson