Use a full path for the framework header include path

Xcode/SDL/pkg-support/resources/CMake/sdl2-config.cmake

@@ -44,7 +44,7 @@ if(NOT TARGET SDL2::SDL2)
     set_target_properties(SDL2::SDL2
         PROPERTIES
             INTERFACE_COMPILE_OPTIONS "-F;${SDL2_FRAMEWORK_PARENT_PATH}"
-            INTERFACE_INCLUDE_DIRECTORIES "SDL2.framework/Headers"
+            INTERFACE_INCLUDE_DIRECTORIES "${SDL2_FRAMEWORK_PARENT_PATH}/SDL2.framework/Headers"
             INTERFACE_LINK_OPTIONS "-F;${SDL2_FRAMEWORK_PARENT_PATH};-framework;SDL2"
     )
 endif()