OS X: Use correct extra path when searching for applicaton bundles (#13066)

The parent commit added a search path relative to OSX_DEVELOPER_ROOT.
But with Xcode 4.3 the nested Applications folder is in a different
relative location compared to that root. This commit makes the intent
of the previous commit work with older and newer Xcode directory layouts.

Furthermore, it only adds paths that exist to the search path.

Modules/Platform/Darwin.cmake

@@ -239,10 +239,22 @@ SET(CMAKE_SYSTEM_FRAMEWORK_PATH
 # default to searching for application bundles first
 SET(CMAKE_FIND_APPBUNDLE FIRST)
 # set up the default search directories for application bundles
+SET(_apps_paths)
+FOREACH(_path
+  "~/Applications"
+  "/Applications"
+  "${OSX_DEVELOPER_ROOT}/../Applications" # Xcode 4.3+
+  "${OSX_DEVELOPER_ROOT}/Applications"    # pre-4.3
+  )
+  GET_FILENAME_COMPONENT(_apps "${_path}" ABSOLUTE)
+  IF(EXISTS "${_apps}")
+    LIST(APPEND _apps_paths "${_apps}")
+  ENDIF()
+ENDFOREACH()
+LIST(REMOVE_DUPLICATES _apps_paths)
 SET(CMAKE_SYSTEM_APPBUNDLE_PATH
-  ~/Applications
-  /Applications
-  ${OSX_DEVELOPER_ROOT}/Applications)
+  ${_apps_paths})
+UNSET(_apps_paths)
 
 INCLUDE(Platform/UnixPaths)
 LIST(APPEND CMAKE_SYSTEM_PREFIX_PATH