libmount: Add 2.40.2 and use Meson

[jwillikers]

Specify library name and version: libmount/2.40.2

The util-linux project is switching to Meson.
This PR switches version 2.40.2 to use Meson instead of Autotools.

Version 2.39 has the following error when cross-compiling under Meson:

libmount/lib_mount.a.p/src_hook_mount.c.o -MF libmount/lib_mount.a.p/src_hook_mount.c.o.d -o libmount/lib_mount.a.p/src_hook_mount.c.o -c ../src/libmount/src/hook_mount.c
../src/libmount/src/hook_mount.c: In function ‘hook_create_mount’:
../src/libmount/src/hook_mount.c:302:40: error: ‘struct statx’ has no member named ‘stx_mnt_id’; did you mean ‘stx_uid’?
  302 |                 cxt->fs->id = (int) st.stx_mnt_id;
      |                                        ^~~~~~~~~~
      |                                        stx_uid

Version 2.40 doesn't hit this snag, so I'm using Meson support for version 2.40.

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• I've read the contributing guidelines.
• I've used a recent Conan client version close to the currently deployed.
• I've tried at least one configuration locally with the conan-center hook activated.

[jwillikers]

I've modified this PR like #20508 to switch to Meson only for the new version 2.40 to avoid cross-compilation problems in 2.39 with Meson. It will be a draft until version 2.40 is released, but the rc2 is working great so far.

[jwillikers]

Hitting this issue: util-linux/util-linux#2830

[conan-center-bot]

Conan v1 pipeline ✔️

All green in build 13 (aa208acad6abdd580c8171639e3a65a6b249f7d5):

• libmount/2.40.2:
  All packages built successfully! (All logs)

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Conan v2 pipeline ✔️

Note: Conan v2 builds are now mandatory. Please read our discussion about it.

All green in build 13 (aa208acad6abdd580c8171639e3a65a6b249f7d5):

• libmount/2.40.2:
  All packages built successfully! (All logs)