MFC r257109: Add clang-CC and CC to list of hints allowing clang to identify its operating mode as c++ instead of defaulting to c for the binary names CC and clang-CC.
MFC r257109:
Add clang-CC and CC to list of hints allowing clang to identify its operating
mode as c++ instead of defaulting to c for the binary names CC and clang-CC.

This fixes builds that use cmake which automatically sets CXX to
/usr/bin/CC by default.

PR:		bin/182442
Approved by:	re (glebius)

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