Fix a regression from 143657.  The second pass of the warning options should only be emitting
warnings/errors for unknown warning options.  getDiagnosticsInGroup returns false if the 
diagnostics is found and true otherwise.  Thus, if we're reporting and we have a valid 
diagnostic, we were actually setting the flag and causing mayhem.
rdar://10444207

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@144670 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Frontend/Warnings.cpp b/lib/Frontend/Warnings.cpp
index 4e41e22..3588af0 100644
--- a/lib/Frontend/Warnings.cpp
+++ b/lib/Frontend/Warnings.cpp
@@ -166,8 +166,9 @@
         continue;
       }
       
-      if (Report && DiagIDs->getDiagnosticsInGroup(Opt, _Diags)) {
-        EmitUnkownDiagWarning(Diags, "-W", Opt, isPositive);
+      if (Report) {
+        if (DiagIDs->getDiagnosticsInGroup(Opt, _Diags))
+          EmitUnkownDiagWarning(Diags, "-W", Opt, isPositive);
       } else {
         Diags.setDiagnosticGroupMapping(Opt, Mapping);
       }