Merge #21298: guix: Bump time-machine, glibc, and linux-headers

c33b199456e57d83c21eacd36d3c56d0a123b0d0 guix: Bump glibc and linux-headers (Carl Dong)
65363a1bd8b886f5aef5fbc97ca88c9c9b243b21 guix: Rebase on 95aca2991b (1.2.0-12.dffc918) (Carl Dong)

Pull request description:

  On bumping the time-machine:

  ```
  A few changes which are useful for us:

  1. 'gnu: cross-gcc-arguments: Enable 128 bit long double for POWER9.' is
     now merged into master.
  2. gnutls is bumped to 3.6.15 and the temporal test failure in
     status-request-revoked is fixed. Note that this does not fix the case
     where one has installed Guix v1.2.0 and is running a substitute-less
     bootstrap build, since the `guix time-machine` command itself has a
     dependency on gnutls v3.6.12 (the one with the broken test) and will
     thus try to build it before attempting to jump forwards in time. This
     does however, mean that those who build a version of Guix that also
     contains this fix will not go backwards in time to build the broken
     gnutls v3.6.12.
  ```

  On bumping the rest:

  ```
  Bump glibc and linux-headers to match those of our Gitian counterparts.

  We also require a glibc >= 2.28 for the test-symbol-check scripts to
  work properly.

  The default BASE-GCC-FOR-LIBC also has to be bumped since glibc 2.31
  requires a gcc >= 6.2
  ```

  This is a prerequisite for #20980

ACKs for top commit:
  fanquake:
    ACK c33b199456e57d83c21eacd36d3c56d0a123b0d0 - I think going ahead with this now and to sycn back up to gitian is fine. It will also unblock #20980. Potential code signing related issues can be sorted out in #21239 and later PRs.

Tree-SHA512: 31f022aadb93ba44813b0da005b1f2e5d67d76e8cdcdb53368924d1ea6cb076a21218c26831a6b0dcdcfe33507f54934330489ba557371d740f5587b7d727b95

contrib/guix/guix-build.sh

@@ -163,7 +163,7 @@ SOURCE_DATE_EPOCH="${SOURCE_DATE_EPOCH:-$(git log --format=%at -1)}"
 time-machine() {
     # shellcheck disable=SC2086
     guix time-machine --url=https://github.com/dongcarl/guix.git \
-                      --commit=6c9d16db962a6f7155571b36eced681fd2889e23 \
+                      --commit=490e39ff303f4f6873a04bfb8253755bdae1b29c \
                       --max-jobs="$MAX_JOBS" \
                       --keep-failed \
                       ${SUBSTITUTE_URLS:+--substitute-urls="$SUBSTITUTE_URLS"} \

contrib/guix/manifest.scm

@@ -126,9 +126,9 @@ chain for " target " development."))
 
 (define* (make-bitcoin-cross-toolchain target
                                   #:key
-                                  (base-gcc-for-libc gcc-5)
-                                  (base-kernel-headers linux-libre-headers-4.19)
-                                  (base-libc glibc-2.27)
+                                  (base-gcc-for-libc gcc-7)
+                                  (base-kernel-headers linux-libre-headers-5.4)
+                                  (base-libc glibc)  ; glibc 2.31
                                   (base-gcc (make-gcc-rpath-link gcc-9)))
   "Convenience wrapper around MAKE-CROSS-TOOLCHAIN with default values
 desirable for building Bitcoin Core release binaries."
@@ -234,12 +234,6 @@ chain for " target " development."))
            (list zip
                  (make-mingw-pthreads-cross-toolchain "x86_64-w64-mingw32")
                  (make-nsis-with-sde-support nsis-x86_64)))
-          ((string-contains target "riscv64-linux-")
-           (list (make-bitcoin-cross-toolchain target
-                                               #:base-gcc-for-libc gcc-7)))
-          ((string-contains target "powerpc64le-linux-")
-           (list (make-bitcoin-cross-toolchain target
-                                               #:base-gcc-for-libc gcc-7)))
           ((string-contains target "-linux-")
            (list (make-bitcoin-cross-toolchain target)))
           ((string-contains target "darwin")