Clippy linting is very slow

I switched to using clippy for linting GPU code in CI and I think it increased CI time by ~8 minutes.
I don't think it should take 8 minutes to run cargo clippy though.

Here is CI run where build.rs for GPU crate was skipping all the work under Clippy: https://github.com/nazar-pc/abundance/actions/runs/21787689837/job/62861720690#step:11:1022
Here is CI run where SpirvBuilder::clippy() is called: https://github.com/nazar-pc/abundance/actions/runs/21905750349/job/63245490660#step:11:1023

Clippy time for ab-farmer crate that includes ab-proof-of-space-gpu as a dependency increased from ~2 minutes to over 10 minutes.

Dependencies for SPIR-V are fairly minimal too and should not take nearly as much time to compile and lint: https://github.com/nazar-pc/abundance/blob/c55eae7482783aea52f0f1e9510e71378c9f10b8/crates/farmer/ab-proof-of-space-gpu/Cargo.toml#L19-L23

I do not know what could it possibly be doing for such a long time, but I do not like it.

Start by comparing the linked CI runs, focusing on build.rs for the GPU crate and the call to SpirvBuilder::clippy(). Inspect the SPIR-V dependencies listed in crates/farmer/ab-proof-of-space-gpu/Cargo.toml. Done means identifying why Clippy adds roughly eight minutes to ab-farmer CI and reducing that regression with evidence from a new run.