ENH: make sure default /System framework is not added with -F

Source/cmGlobalXCodeGenerator.cxx

@@ -1287,6 +1287,7 @@ void cmGlobalXCodeGenerator::CreateBuildSettings(cmTarget& target,
   std::vector<std::string>::iterator i = includes.begin();
   std::string fdirs;
   std::set<cmStdString> emitted;
+  emitted.insert("/System/Library/Frameworks");
   for(;i != includes.end(); ++i)
     {
     if(cmSystemTools::IsPathToFramework(i->c_str()))

Source/cmLocalGenerator.cxx

@@ -1084,6 +1084,9 @@ const char* cmLocalGenerator::GetIncludeFlags(const char* lang)
 
   bool flagUsed = false;
   std::set<cmStdString> emitted;
+#ifdef __APPLE__
+  emitted.insert("/System/Library/Frameworks");
+#endif
   for(i = includes.begin(); i != includes.end(); ++i)
     {
 #ifdef __APPLE__

Source/cmMakefileTargetGenerator.cxx

@@ -1116,6 +1116,7 @@ std::string cmMakefileTargetGenerator::GetFrameworkFlags()
   return std::string();
 #else
   std::set<cmStdString> emitted;
+  emitted.insert("/System/Library/Frameworks");
   std::vector<std::string> includes;
   this->LocalGenerator->GetIncludeDirectories(includes);
   std::vector<std::string>::iterator i;