If we would set RUSTC to something like /cargo-miri-phase-rustc/if-you-see-this-some-build-script-forgot-to-apply-the-rustc-wrapper, then it would be blindingly obvious if anything ever bypassed our RUSTC_WRAPPER and called rustc directly. This kind of bypass is something we don't want to happen as then we can't carefully adjust the command-line flags to make everything work with Miri.

Unfortunately, this is currently blocked:

• autocfg: autocfg still calls rustc without the wrapper cuviper/autocfg#58
• eyre: build.rs probe fails to propagate --target and does not use RUSTC_WRAPPER eyre-rs/eyre#84
• cargo itself: RUSTC_WRAPPER is ignored for rustc -vV call cargo#10885