meson broken by update to Python 3.13

[bonzini]

Description / Steps to reproduce the issue

Meson was never tested on Windows hosts with Python 3.13, but it relied on os.path.isabs return true for paths without a drive---mostly to be able to correctly detect paths outside a tree.

As visible (for example) here, the change to os.path.isabs semantics in Python 3.13 breaks everything quite horribly.

Expected behavior

Until this is fixed, it can cause chain failures in building packages that use meson (and of course also problems for users).

Actual behavior

N/A

Verification

• I have verified that my MSYS2 is up-to-date before submitting the report (see https://www.msys2.org/docs/updating/)

Windows Version

MINGW32_NT-10.0-20348

Are you willing to submit a PR?

Not directly to MSYS2, but there is a Meson PR in progress at mesonbuild/meson#15464. I'm not sure if it will be included in the upcoming 1.10.1 release.

[bonzini]

Reporting this here, even though it's really just an upstream problem, because of the effects this has on MSYS2 packagers.

[lazka]

Thanks, this was already patched during the package rebuild: https://github.com/msys2/MINGW-packages/blob/35ca9f249f96e1ee9c24dee2e88ecc399d2fcced/mingw-w64-meson/0006-allow-drive-relative-prefix.patch

We only use these types of paths as prefix, so the patching required was limited.

[bonzini]

Based on the upstream patch, the install part is incomplete apart from the other more obscure cases (at least the test_pkgconfig_gen_escaping testcase should be broken).

Of course you don't care too much (for example) about cases where the new isabs accepts meson.build file that should be rejected.