Gtk2 build fails on MacOS 10.12 and later: ./gdkaliasdef.c:220:102: error: aliases are not supported on darwin

On 10.15, gdkaliasdefs.c raises a bunch of error: aliases are not supported on darwin. Interestingly on 10.12 the error is only weak aliases are supported on darwin and there's no problem on 10.11 and earlier. Those aliases have been around for 20 years, so it's from a change in Apple's version of clang or in the MacOS SDK. @samm-git have you encountered this?