CMake: Fix Blender.app creation/modification time

It was failing on first run of CMake since the Blender.app is not yet
created.

source/creator/CMakeLists.txt

@@ -921,6 +921,11 @@ elseif(APPLE)
   OUTPUT_STRIP_TRAILING_WHITESPACE)
 
   # Give the bundle actual creation/modification date
+  #
+  # Note that the directory might not yet exist, which happens when CMake is first run.
+  if(NOT EXISTS ${EXECUTABLE_OUTPUT_PATH}/Blender.app)
+    file(MAKE_DIRECTORY ${EXECUTABLE_OUTPUT_PATH}/Blender.app)
+  endif()
   execute_process(COMMAND SetFile -d ${SETFILE_DATE} -m ${SETFILE_DATE}
                   ${EXECUTABLE_OUTPUT_PATH}/Blender.app)