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

[via cfe-commits]

================
@@ -1697,6 +1698,15 @@ ASTContext::getRelocationInfoForCXXRecord(const CXXRecordDecl *RD) const {
   return std::nullopt;
 }
 
+void ASTContext::initSanitizers(const LangOptions &LangOpts,
+                                SourceManager &SM) {
+  std::string Error;
+  if (!NoSanitizeL->init(LangOpts.NoSanitizeFiles, Error)) {
+    const std::string &Path = LangOpts.NoSanitizeFiles.front();
----------------
woruyu wrote:

> Custom diagnostics are not an acceptable solution IMO;

Thanks for the feedback! To confirm: is the correct fix to define dedicated diagnostics in a `.td` file like this:
```
def err_no_sanitize_file_open_fail : Error<
  "failed to load NoSanitize file: can't open file '%0'">;

def err_no_sanitize_file_parse_fail : Error<
  "failed to load NoSanitize file: error parsing file '%0'">;

def SanitizeIgnorelist : DiagGroup<"sanitize-ignorelist">;
```
Then use them accordingly in `ASTContext::initSanitizers`.

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