[Clang] Add option to disable -mconstructor-aliases with -mno-constructor-aliases

We've found that when profiling, counts are only generated for the real definition of constructor aliases (C2 in mangled name). However, when compiling the C1 version is present at the callsite and leads to a lack of counts due to this aliasing. This causes us to miss out on inlining an otherwise hot constructor.

-mconstructor-aliases is AFAICT an optimization, so having a disabling flag if wanted seems valuable.

Testing:
ninja check-all

Reviewed By: wenlei

Differential Revision: https://reviews.llvm.org/D114130