meson: update to 1.12.0

[sjozs]

Testing the changes

• I tested the changes in this PR: YES

Did the same tests as with #61424.

nix now compiles, there was a single regression with corecollector (D compilers got C-like ldflags in sanity check, which led to "dmd cannot compile programs") with a single-line upstream patch, so I added that. I compiled every package on x86_64 with "meson" in its template, fixed anything easily fixable (eg. Codeberg tarball checksum instability), the rest is here:

citations - appdata validation fails, upstream problem - might be fixed by a new AppStream version?
ddgtk - bad appstream file, upstream problem
gamescope - broken compilation with libinput 1.31, there are lots of new upstream releases but I'm not using the package
gnome-authenticator - warnings in metainfo file
gnome-calculator - will be fixed in 51.0, used library (MPC) changed sign of sqrt(negative number), see https://gitlab.gnome.org/GNOME/gnome-calculator/-/work_items/531
gst-plugins-rs1 - compilation broken with new Rust, 0.15 (or at least 0.13.7) available
gxml - upstream bug: https://gitlab.gnome.org/GNOME/gxml/-/work_items/49
io.elementary.files - very old version broken with new gcc+vala, upstream bug: https://github.com/elementary/files/issues/2508
iputils - raw sockets disabled, ping tests fail
kiwix-lib - see: https://github.com/kiwix/libkiwix/issues/1266#issuecomment-4352527068 (upstream patched already)
libgweather - upstream bug: https://gitlab.gnome.org/GNOME/libgweather/-/work_items/348 (metar network dependency changed)
libupnpp - 1.0.3 source tarball has disappeared, I couldn't find why
libvarlink - broken tests, seemingly for a long time (actually, it seems like it passes more of JSONTestSuite than the tests expect)
localsearch - eg. missing man from checkdepends (other errors were independent from meson version)
newsflash - bad checksum
open-isns - same bug as with older meson
p11-kit - no idea but couldn't fix, broken in old meson too (most likely suid-related)
pacman - cross-meson-version consistent broken tests
pango - consistently broken tests
patchmatrix - code hosting site down since at most January
pcsc-ccid - distfiles gone (looks like only the last 3 is kept on server)
python3-pywt - cross-meson broken tests
rest - test depends on flickr, broken with either meson version
sagemath - Cython error while compiling: list.to_py:145:30: Cannot convert 'list[T]' to Python object (meson version does not change anything)
switchboard - bad checksum, code from 2022, practically unmaintained package
switchboard-plug-bluetooth - same
switchboard-plug-network - same
switchboard-plug-printers - same
tinysparql - meson-independently broken tests in 'core+slow - tinysparql:sparql'
umockdev - deprecation inside glib import code+-Werror::DeprecationWarning
virt-manager - yep, tests fail (independent upstream problem)
xorg-server - GLX extension missing in bug1354-gl(es) tests, not meson-related
zathura - aborts in xbps-src (any meson version), works locally

As far as I can see, there were no surprises since my last attempt in #61424.