[compiler-rt] [compiler-rt] Fix C and C++ compilers being switched when compiling tests (PR #110552)

[Alexander Richardson via llvm-commits]

https://github.com/arichardson approved this pull request.

Good catch, I guess it didn't matter in most cases since clang will parse .cc files as C++ by default.

https://github.com/llvm/llvm-project/pull/110552