Xcode: Call IsCFBundleOnApple to decide if bundle is being built

Narrow down the decision if a CFBundle is built to one place.
This is a preparation patch to add another target property
which, if set, will imply BUNDLE.  Having only one function
which will have to look at both properties helps to keep code
clean.

Signed-off-by: Gregor Jasny <[email protected]>

Source/cmGlobalXCodeGenerator.cxx

@@ -1925,7 +1925,7 @@ void cmGlobalXCodeGenerator::CreateBuildSettings(cmTarget& target,
     {
     buildSettings->AddAttribute("LIBRARY_STYLE",
                                 this->CreateString("BUNDLE"));
-    if (target.GetPropertyAsBool("BUNDLE"))
+    if (target.IsCFBundleOnApple())
       {
       // It turns out that a BUNDLE is basically the same
       // in many ways as an application bundle, as far as