[HIP] Fix job action offloading kind for mixed HIP/C++ compilation

When both HIP and C++ programs are input files to clang
with -c, clang treats C++ programs as HIP programs,
which is incorrect.

This is due to action builder does not set correct
offloading kind for job actions for C++ programs.

Reviewed by: Artem Belevich

Differential Revision: https://reviews.llvm.org/D120910