This patch takes the suggestion by Sean Silva in https://reviews.llvm.org/D17622 to decouple cc1 option from driver level option.
-fprofile-instr-use={} is now a driver only option. The cc1 part is replaced by -fprofile-instrument-use={llvm,clang}.
It sets a CodeGenOpt ProfileUse which is either {None, Clang, LLVM}, a common enum for -fprofile-instrument={} (for the profile instrument).
The profile path cc1 option now becomes -fprofile-instrument-usepath={}.
Small bikeshed: usepath reads weird to me. Can we make it use-path?