cmake: get_filename_component(EXT) returns extension including leading dot

CMakeLists.txt

@@ -3123,7 +3123,7 @@ endif()
 if(APPLE)
   foreach(SOURCE_FILE ${SOURCE_FILES})
     get_filename_component(FILE_EXTENSION ${SOURCE_FILE} EXT)
-    if(FILE_EXTENSION STREQUAL "m")
+    if(FILE_EXTENSION STREQUAL ".m")
       set_property(SOURCE ${SOURCE_FILE} APPEND_STRING PROPERTY COMPILE_FLAGS " -x objective-c")
     endif()
   endforeach()