GHS: Set LANGUAGE type for source files

Use gbuild project syntax for setting the language type for the file.
gbuild will pick the correct compiler or tool to use.

NOTE: Language names come from gbuild config files.  Therefore to
compile a file with the C++ compiler use "C++" not "CXX".

The previous implementation was passing the C compiler a flag to compile as C++
if LANGUAGE was set to "CXX".

Source/cmGhsMultiTargetGenerator.h

@@ -65,8 +65,7 @@ private:
   void WriteSourceProperty(std::ostream& fout, const cmSourceFile* sf,
                            std::string const& propName,
                            std::string const& propFlag);
-  static void WriteObjectLangOverride(std::ostream& fout,
-                                      const cmSourceFile* sourceFile);
+  static std::string WriteObjectLangOverride(const cmSourceFile* sourceFile);
 
   bool DetermineIfIntegrityApp();
   cmGeneratorTarget* GeneratorTarget;