[llvm] [ctxprof] Extend the notion of "cannot return" (PR #135651)

[Mircea Trofin via llvm-commits]

================
@@ -105,6 +106,12 @@ std::pair<uint32_t, uint32_t> getNumCountersAndCallsites(const Function &F) {
   }
   return {NumCounters, NumCallsites};
 }
+
+void emitUnsupportedRoot(const Function &F, StringRef Reason) {
----------------
mtrofin wrote:

the root is unsupported. `emitUnsupportedRootError` is probably what we want.

https://github.com/llvm/llvm-project/pull/135651