This adds a very minimalistic (in terms of functionality and
dependencies) test for wlroots, Wayland, and related packages.
The Sway test covers more functionality and packages (e.g. XWayland) but
this test has tree advantages:
- Less dependencies: Much fewer rebuilds are required when testing core
changes that need to go through staging.
- Testing wlroots updates: The Sway package isn't immediately updated
after a new wlroots version is released and a lot of other packages
depend on wlroots as well.
- Determining whether a bug only affects Sway or wlroots/TinyWL as well.
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