Auto merge of #63470 - Mark-Simulacrum:rustc-depdep, r=alexcrichton

Utilize -Zbinary-dep-depinfo in rustbuild

We no longer utilize stamp-file mtimes at all inside rustbuild, and a future PR may be able to entirely eliminate them by eagerly copying to the appropriate sysroot. The only mtime-based dependency tracking left is for documentation because we lie to Cargo about the rustdoc binary, so Cargo does not track changes to the real binary, and codegen-backends because binary-dep-depinfo does not emit that information into the depfiles.

Both of these are fixable in the longer term but this existing patch gives us the following benefits:
 * We no longer delete Cargo target directories manually within a stage. Cross-stage, changes to codegen backends will still clear out target directories. This means that incremental state persists across individual steps (e.g., rebuilding libstd does not clear out librustc incremental state). Fixes #54712.
 * Dependency tracking across steps within a given stage is now fully precise. We will not clear out all codegen backend dependencies due to changes in librustc_driver, for example, only deleting the final librustc_codegen_llvm crate. Fixes #54008, fixes #50481.
 * We properly track codegen backends as a dependency (equivalent to rustc) across changes. Fixes #53284, and fixes #52719.
 * Cross-stage dependency tracking of crates is also much more accurate and reliable. Most likely fixes #49979 (but no reproduction steps in that issue). Fixes #59105.

cc #63012

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