Merge bitcoin#24042: build: Point Guix to the current top of the "version-1.4.0" branch

a229451 build: Point Guix to the current top of the "version-1.4.0" branch (Hennadii Stepanov)

Pull request description:

  On master (c561f2f) the commit in Guix repo from bitcoin#23778 seems unavailable:
  ```
  $ git checkout fa17abf1af09570708daa28dd40ffbc932ebe25c
  fatal: reference is not a tree: fa17abf1af09570708daa28dd40ffbc932ebe25c
  ```

  This PR points Guix to the current top of the "version-1.4.0" branch.

  Fixes bitcoin#24040.

ACKs for top commit:
  MarcoFalke:
    Approach ACK a229451
  fanquake:
    ACK a229451 - from what I've seen on the mailing list there shouldn't be any more force pushing.

Tree-SHA512: c58f846fb0afd51b5c2dd33034e9d593aec5d5b49e9f2232af70ae1224da8408ad4e05aa314609350d92a6400e354a816b988226e3572198c3f839ab33913164

Author: fanquake

contrib/guix/guix-build

@@ -239,7 +239,7 @@ SOURCE_DATE_EPOCH="${SOURCE_DATE_EPOCH:-$(git -c log.showSignature=false log --f
 time-machine() {
     # shellcheck disable=SC2086
     guix time-machine --url=https://git.savannah.gnu.org/git/guix.git \
-                      --commit=fa17abf1af09570708daa28dd40ffbc932ebe25c \
+                      --commit=6ba510d76d6847065be725e958718002f3b13c7a \
                       --cores="$JOBS" \
                       --keep-failed \
                       --fallback \