ENH: fix problems with .def and RC files

Modules/CMakeRCInformation.cmake

@@ -15,7 +15,7 @@ SET (CMAKE_RC_FLAGS "${CMAKE_RC_FLAGS_ENV_INIT} $ENV{RCFLAGS} ${CMAKE_RC_FLAGS_I
 
 # now define the following rule variables
 # CMAKE_RC_COMPILE_OBJECT
-
+SET(CMAKE_INCLUDE_FLAG_RC "-I")
 # compile a Resource file into an object file
 IF(NOT CMAKE_RC_COMPILE_OBJECT)
   SET(CMAKE_RC_COMPILE_OBJECT

Source/cmGlobalGenerator.cxx

@@ -312,6 +312,10 @@ void cmGlobalGenerator::EnableLanguage(std::vector<std::string>const& languages,
 
 const char* cmGlobalGenerator::GetLanguageOutputExtensionForLanguage(const char* lang)
 {
+  if(!lang) 
+    {
+    return "";
+    }
   if(m_LanguageToOutputExtension.count(lang) > 0)
     {
     return m_LanguageToOutputExtension[lang].c_str();
@@ -321,6 +325,10 @@ const char* cmGlobalGenerator::GetLanguageOutputExtensionForLanguage(const char*
 
 const char* cmGlobalGenerator::GetLanguageOutputExtensionFromExtension(const char* ext)
 {
+  if(!ext)
+    {
+    return "";
+    }
   const char* lang = this->GetLanguageFromExtension(ext);
   return this->GetLanguageOutputExtensionForLanguage(lang);
 }