[clang] [llvm] fix: replace report_fatal_error with Diags and exit (PR #147959)

[Aaron Ballman via cfe-commits]

AaronBallman wrote:

Reverting the changes because these failures look related to the patch. I *think* we're missing a call to `initSanitizers()` somewhere, possibly in `SanitizerSpecialCaseList::create()`. I don't have the bandwidth to try to debug it now, hence the revert.

https://github.com/llvm/llvm-project/pull/147959