ENH: fix double CMAKE_(LANG)_FLAGS problem in try compile

Source/cmTryCompileCommand.cxx

@@ -175,7 +175,7 @@ int cmTryCompileCommand::CoreTryCompileCode(
     langFlags +=  lang;
     langFlags += "_FLAGS";
     fprintf(fout, "SET(CMAKE_VERBOSE_MAKEFILE 1)\n");
-    fprintf(fout, "SET(CMAKE_%s_FLAGS \"${CMAKE_%s_FLAGS}", lang, lang);
+    fprintf(fout, "SET(CMAKE_%s_FLAGS \"", lang);
     const char* flags = mf->GetDefinition(langFlags.c_str()); 
     if(flags)
       {