Introduce -enable-global-analyses to allow users to disable inter-procedural analyses

Alive2 doesn't support verification of optimizations that use inter-procedural analyses.
Right now, clang uses GlobalsAA by default and there's no way to disable it.
This leads to Alive2 producing false positives.
The added flag allows us to skip global analyses altogether.

Differential Revision: https://reviews.llvm.org/D134139