qualify if llvm is really needed for asahi VIDEO_CARD

[Kokokokoka]

If one uses rust-gpu for asahi, mesa should work even without llvm (more than that, it works without llvm flag). why is llvm dependency added?

[jannau]

I was mistaken and llvm/spirv/libclc are only build dependencies

[jannau]

I changed libclc to a build dependency but I won't touch llvm. It is an build dependency but I would prefer not to touch the complicated dependency handling for llvm

[Kokokokoka]

dunno why, it is working without llvm dep (i remove manually it every time)