CC from environment is used to initialize CMAKE_C_COMPILER so
setting CMAKE_C_COMPILER explicitly isn't needed.
The syntax in ci_build.bash was broken in case one wished to put
spaces in CC.
(cherry picked from commit 0c1e6d900b)
We discussed the name and it's less cognitive load to just call it '.bash'
so you don't have an immediate question about if bashisms are OK.
(cherry picked from commit 73f629e321)