[WIP] linker: also dump SPIR-T on panic, not just during successful compilation.

[eddyb]

This is the idea I mentioned in:

• https://github.com/EmbarkStudios/rust-gpu/issues/1086#issuecomment-1655044334

However, opening as draft because the situation is even messier than envisioned and more panic handling is needed (up to an including potentially enabling fine-grained dumping without the user requesting it, by running the SPIR-T pipeline again, starting from the same SPIR-V blob, if the initial attempt ended in a panic - care would need to be taken for diagnostics or the panic itself, to not be redundantly reported).