Issue 53878, v3. See <https://issues.guix.gnu.org/53878#72>. Changes since v2: * 05/15: Fix typo in commit message. * 09/15: Add `%racket-version` and `%racket-origin`. * 11/15: Add `%chez-scheme-for-racket-version`. * 15/15: Use `%racket-version` and `%racket-origin`. Also: * `racket-minimal`: The package to install explicitly is "racket-lib" ("base" is implicit). * `make-installation-layer.rkt`: Adjust workaround for <https://github.com/racket/racket/issues/4133>, because `racket` (but not `racket-minimal`) ends up actually creating the bogus untethered "bin" directory.