Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/6931>
This is a hard error starting with Meson 0.60.0rc1, due to https://github.com/mesonbuild/meson/pull/9184#issuecomment-941603358 The upstream change might get reverted before release, but we should of course fix this regardless. Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/1127>