Add Librashader support

[ghost]

This is a mostly complete PR for adding Librashader support. It compiles and copies librashader.so andlibrashader.pc to the appropriate directories. However, the ares Flatpak does not seem to be picking up these files.

I couldn't figure this last part out so I figured I'd open a PR and mark it as a draft to see if anyone could help get this addition over the last hurdle.

Closes https://github.com/flathub/dev.ares.ares/issues/36

Upstream issue: https://github.com/ares-emulator/ares/issues/1608

[flathubbot]

Started test build 140796

[flathubbot]

Build 140796 successful To test this build, install it from the testing repository:

flatpak install --user https://dl.flathub.org/build-repo/123844/dev.ares.ares.flatpakref

[flathubbot]

Started test build 142987

[flathubbot]

Build 142987 successful To test this build, install it from the testing repository:

flatpak install --user https://dl.flathub.org/build-repo/126040/dev.ares.ares.flatpakref

[flathubbot]

Started test build 142992

[flathubbot]

Build 142992 successful To test this build, install it from the testing repository:

flatpak install --user https://dl.flathub.org/build-repo/126045/dev.ares.ares.flatpakref