[UBSan] Enable 'help' option output, report unrecognized flags

Summary:
Let UBSan output flag description if 'help' options is provided.
Report unrecognized flags if verbosity mode is turned on.

Patch by Svetlana Ryabkova!

Differential Revision: http://reviews.llvm.org/D11903

llvm-svn: 244946

compiler-rt/lib/ubsan/ubsan_flags.cc

@@ -60,6 +60,9 @@ void InitializeFlags() {
   // Override from environment variable.
   parser.ParseString(GetEnv("UBSAN_OPTIONS"));
   SetVerbosity(common_flags()->verbosity);
+  if (Verbosity()) ReportUnrecognizedFlags();
+
+  if (common_flags()->help) parser.PrintFlagDescriptions();
 }
 
 }  // namespace __ubsan