ENH: Simplify framework -F flag generation

This removes an unnecessary use of ConvertToOutputForExisting which is
needed only on Windows to consider short-pathing.

Source/cmLocalGenerator.cxx

@@ -1155,9 +1155,11 @@ const char* cmLocalGenerator::GetIncludeFlags(const char* lang)
       frameworkDir = cmSystemTools::CollapseFullPath(frameworkDir.c_str());
       if(emitted.insert(frameworkDir).second)
         {
-        includeFlags 
-          << "-F" 
-          << this->ConvertToOutputForExisting(frameworkDir.c_str()) << " ";
+        includeFlags
+          << "-F" << this->Convert(frameworkDir.c_str(),
+                                   cmLocalGenerator::START_OUTPUT,
+                                   cmLocalGenerator::SHELL, true)
+          << " ";
         }
       continue;
       }

Source/cmMakefileTargetGenerator.cxx

@@ -1452,7 +1452,9 @@ std::string cmMakefileTargetGenerator::GetFrameworkFlags()
     if(emitted.insert(*i).second)
       {
       flags += "-F";
-      flags += this->LocalGenerator->ConvertToOutputForExisting(i->c_str());
+      flags += this->Convert(i->c_str(),
+                             cmLocalGenerator::START_OUTPUT,
+                             cmLocalGenerator::SHELL, true);
       flags += " ";
       }
     }