[BOLT] Reduce CFI warning verbosity (#105336)

CFI programs may have more saves than restores and this is completely
benign from BOLT's perspective. Reduce the verbosity and print the
warning only under `-v=1` and above.

Author: maksfb

bolt/lib/Core/BinaryFunction.cpp

@@ -2502,7 +2502,7 @@ void BinaryFunction::annotateCFIState() {
     }
   }
 
-  if (!StateStack.empty()) {
+  if (opts::Verbosity >= 1 && !StateStack.empty()) {
     BC.errs() << "BOLT-WARNING: non-empty CFI stack at the end of " << *this
               << '\n';
   }