Fix linking errors where paths not being found cause link errors with prebuilt clang
This is a default Qualcomm llvm/clang flag as well.

Change-Id: I42d5ecde579fe3f3cd36bff88ca30a2c0d6c4489
Add use_clang for new sources, rather than switching all with LOCAL_CLANG := true

Change-Id: I0f6a528c47ef00ac93ee43f1c1b1603c150c9be5