Add Librashader support

[ghost]

This is a mostly complete PR for adding Librashader support. It compiles and copies librashader.so and librashader.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 #36

Upstream issue: ares-emulator/ares#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