ci: Re-add explicit Meson version to Alpine CI image
Alpine 3.19 ships with Meson 1.3.0, which has broken handling of File objects and their paths. This causes (as far as I can tell) un-work-around-able breakage of GLib’s build.
See https://github.com/mesonbuild/meson/issues/5273#issuecomment-1851811417
That should be fixed in Meson 1.4.0, but that might not be released for a while. Because we’re here to test GLib, not Meson, let’s pin the Meson version in the Alpine CI image to 1.2.3, which we know works and is reasonably up to date (and is what the other CI images use).
Fixes this CI failure: https://gitlab.gnome.org/GNOME/glib/-/jobs/3361388
Signed-off-by: Philip Withnall pwithnall@gnome.org