[Nomadcxx]

Closes #57551.

Includes gslapper as a missing runtime dependency.

sysc-greet's source code is GPL-3.0-only. THIRD_PARTY_NOTICES.md covers third-party code and model assets supplied through sysc-Go.

gslapper is also an optional backend for Waypaper and Waytrogen, and a runtime dependency of Noctalia's gSlapper wallpaper plugin.

New package

• This new package conforms to the package requirements: YES

Testing the changes

• I tested the changes in this PR: YES
• I also tested sysc-greet on a live desktop outside a VM.
• Clean Void glibc VM (1.3.0): package installation, cagebreak greeter, niri login, F4 reboot and shutdown.
• gSlapper: PNG, JPEG, WebP, MP4 and WebM playback.

Local build testing

• x86_64-glibc and x86_64-musl: xlint and xbps-src -Q passed for gslapper 1.5.4 and sysc-greet 1.3.2, including gslapper's Meson tests and sysc-greet's Go tests.

Notes

• sysc-greet includes activation instructions for greetd's _greeter account.

[Nomadcxx]

Bumped to gslapper 1.5.4 and sysc-greet 1.3.2 and rebased on master. gSlapper carries the musl mtrace fix upstream now, so I dropped the patch.

Heads up, every meson package currently fails on master with the b_ndebug error from #63557, so gslapper will hit it in CI until that's fixed. With 59af1a4 reverted locally, both packages build and pass their tests on x86_64 glibc and musl.

The CI run is still waiting on approval, could someone kick it off when you get a chance?

Cheers