[Migrated] spirv-builder should declare dependencies on Cargo.toml files.

Issue automatically imported from old repo: https://github.com/EmbarkStudios/rust-gpu/issues/404
Old labels: t: enhancement,s: needs update
Originally creatd by eddyb on 2021-02-01T12:18:03Z

For #403 I changed the workspace Cargo.toml, but that didn't result in a rebuild of sky-shader, whereas something like this does cause a rebuild (of example-runner-wgpu, in this example):

[profile.dev.package."example-runner-wgpu"]
opt-level = 3

So I think we need spirv-builder to get the workspace Cargo.toml (and Cargo.lock, I suppose) paths from Cargo somehow, and also list those out as "rebuild if changed".

Inizia tracciando spirv-builder e il modo in cui ottiene i metadati Cargo per sky-shader, quindi confronta il comportamento di Cargo.toml e Cargo.lock del workspace con il caso example-runner-wgpu descritto nell’issue. Verifica come Cargo contrassegna i file per una ricompilazione e aggiungi o aggiorna una copertura mirata in modo che le modifiche al manifest del workspace attivino la ricompilazione prevista.