* gnu/packages/rust.scm (rust): Update to 1.67.
[arguments]: Add a phase to skip tests requiring mercurial. Extend the
custom 'patch-process-tests phase.
(rust-1.64)[arguments]: Adjust 'patch-cargo-checksums phase to patch
another file.
* guix/build/cargo-build-system.scm (package): Adjust to remove
Cargo.toml.orig file if it exists.