Add toggling for -fnew-infallible/-fno-new-infallible

Allow toggling of -fnew-infallible so last instance takes precedence

Testing:
ninja check-all

Reviewed By: bruno

Differential Revision: https://reviews.llvm.org/D113523

GitOrigin-RevId: 47f230ba2c8ff0e45e025163862ad699746b0ab0
5 files changed