This means we can depend on fix 42ba8efaf2 in Meson, which fixes use of
`volatile` in the default templates used by `gnome.mkenums_simple()`.
This fixes compiler warnings with recent compilers, which are promoted
to errors due to `-Werror`.
Meson 0.57.0 is available in bullseye-backports in Debian, which means
it’s available basically everywhere now.
Bumping the dependency required fixing a few deprecations in the
`meson.build` files.
Signed-off-by: Philip Withnall <pwithnall@endlessos.org>
0bbdb242a0