This patch is taken from Debian, using Debian version 1.7.0-8.
A new patch will be needed when apr is updated.

# quick and dirty fix for FTBFS on mipsel
# There should be a proper configure check, see 
# https://bz.apache.org/bugzilla/show_bug.cgi?id=63566
Index: apr-1.7.0/include/arch/unix/apr_arch_atomic.h
===================================================================
--- apr-1.7.0.orig/include/arch/unix/apr_arch_atomic.h
+++ apr-1.7.0/include/arch/unix/apr_arch_atomic.h
@@ -26,6 +26,9 @@
 /* noop */
 #elif HAVE_ATOMIC_BUILTINS
 #   define USE_ATOMICS_BUILTINS
+#   if (__INTPTR_WIDTH__ == 32) && ( defined(__MIPSEL__) || defined(__powerpc__) ) || defined(__m68k__) || defined(__sh__)
+#       define NEED_ATOMICS_GENERIC64
+#   endif
 #elif defined(SOLARIS2) && SOLARIS2 >= 10
 #   define USE_ATOMICS_SOLARIS
 #   define NEED_ATOMICS_GENERIC64
Index: apr-1.7.0/atomic/unix/builtins64.c
===================================================================
--- apr-1.7.0.orig/atomic/unix/builtins64.c
+++ apr-1.7.0/atomic/unix/builtins64.c
@@ -16,7 +16,7 @@
 
 #include "apr_arch_atomic.h"
 
-#ifdef USE_ATOMICS_BUILTINS
+#if defined(USE_ATOMICS_BUILTINS) && ! defined(NEED_ATOMICS_GENERIC64)
 
 APR_DECLARE(apr_uint64_t) apr_atomic_read64(volatile apr_uint64_t *mem)
 {
Index: apr-1.7.0/atomic/unix/builtins.c
===================================================================
--- apr-1.7.0.orig/atomic/unix/builtins.c
+++ apr-1.7.0/atomic/unix/builtins.c
@@ -20,7 +20,11 @@
 
 APR_DECLARE(apr_status_t) apr_atomic_init(apr_pool_t *p)
 {
+#if defined (NEED_ATOMICS_GENERIC64)
+    return apr__atomic_generic64_init(p);
+#else
     return APR_SUCCESS;
+#endif
 }
 
 APR_DECLARE(apr_uint32_t) apr_atomic_read32(volatile apr_uint32_t *mem)
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<div class='path'>path: <a href='/guix/log/?id=6995d6843596e38e4452a8b775d572dd2f26c64b'>root</a>/<a href='/guix/log/gnu?id=6995d6843596e38e4452a8b775d572dd2f26c64b'>gnu</a>/<a href='/guix/log/gnu/machine?id=6995d6843596e38e4452a8b775d572dd2f26c64b'>machine</a>/<a href='/guix/log/gnu/machine/ssh.scm?id=6995d6843596e38e4452a8b775d572dd2f26c64b'>ssh.scm</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/gnu/machine/ssh.scm?id=6995d6843596e38e4452a8b775d572dd2f26c64b&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2022-03-01 10:30:17 -0500'>2022-03-01</span></td><td><a href='/guix/commit/gnu/machine/ssh.scm?id=0dc019e19a23fea614be5623360849ab9bc35e74'>initrd: Use non-hyphenated kernel command-line parameter names.</a><span class='msg-avail'>...<span class='msg-tooltip'>This is to make it less surprising, given the common convention sets forth by
the kernel Linux command-line parameters.

* gnu/build/linux-boot.scm (boot-system): Rename '--load', '--repl', '--root'
and '--system' to 'gnu.load', 'gnu.repl', 'root' and 'gnu.system',
respectively.  Adjust doc.
(find-long-option): Adjust doc.
* gnu/installer/parted.scm (installer-root-partition-path): Adjust accordingly.
* gnu/system.scm (bootable-kernel-arguments): Add a VERSION argument and
update doc.  Use VERSION to conditionally return old style vs new style initrd
arguments.
(%boot-parameters-version): Increment to 1.
(operating-system-boot-parameters): Adjust doc.
(operating-system-boot-parameters-file): Likewise.
* gnu/system/linux-initrd.scm (raw-initrd, base-initrd): Likewise.
* doc/guix.texi: Adjust doc.
* gnu/build/activation.scm (boot-time-system): Adjust accordingly.
* gnu/build/hurd-boot.scm (boot-hurd-system): Likewise.
* gnu/packages/commencement.scm (%final-inputs-riscv64): Adjust comment.
</span></span></td><td>Maxim Cournoyer</td></tr>
<tr><td><span title='2022-01-16 23:56:55 +0100'>2022-01-16</span></td><td><a href='/guix/commit/gnu/machine/ssh.scm?id=084b76a70a6b302529f3450e6d07f1d105a10f7d'>machine: ssh: Add 'safety-checks?' field.</a><span class='msg-avail'>...<span class='msg-tooltip'>Fixes &lt;https://issues.guix.gnu.org/52766&gt;.
Reported by Michael Rohleder &lt;mike@rohleder.de&gt;.

* gnu/machine/ssh.scm (&lt;machine-ssh-configuration&gt;)[safety-checks?]: New
field.
(machine-check-file-system-availability): Return the empty list when
'safety-checks?' is false.
(machine-check-initrd-modules): Likewise.
* doc/guix.texi (Invoking guix deploy): Document it.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2022-01-09 23:17:17 +0100'>2022-01-09</span></td><td><a href='/guix/commit/gnu/machine/ssh.scm?id=7f20e59a13a6acc3331e04185b8f1ed2538dcd0a'>machine: ssh: Open a single SSH session per machine.</a><span class='msg-avail'>...<span class='msg-tooltip'>Previously, any call to 'managed-host-remote-eval' and similar would
open a new SSH session to the host.  With this change, an SSH session is
opened once, cached, and then reused by all subsequent calls to
'machine-ssh-session'.

* gnu/machine/ssh.scm (&lt;machine-ssh-configuration&gt;): Add
'this-machine-ssh-configuration'.
[session]: Mark as thunked and change default value to an
'open-machine-ssh-session*' call.
(open-machine-ssh-session, open-machine-ssh-session*): New procedures.
(machine-ssh-session): Replace inline code by call to
'open-machine-ssh-session'.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2021-06-03 13:04:20 +0200'>2021-06-03</span></td><td><a href='/guix/commit/gnu/machine/ssh.scm?id=fe509e017fa1c0e3d0b057784b081def3aa621ad'>machine: ssh: Respect calling convention for monadic procedures.</a><span class='msg-avail'>...<span class='msg-tooltip'>Fixes a regression introduced in
2885c3568edec35086f8feeae5b60259cbea407c.

Reported by Mathieu Othacehe.

* gnu/machine/ssh.scm (deploy-managed-host)[eval/error-handling]: Return
two values in the standard case.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2021-06-01 23:26:07 +0200'>2021-06-01</span></td><td><a href='/guix/commit/gnu/machine/ssh.scm?id=2885c3568edec35086f8feeae5b60259cbea407c'>machine: ssh: Gracefully handle failure of the effectful bits.</a><span class='msg-avail'>...<span class='msg-tooltip'>Previously, '&amp;inferior-exception' raised by 'upgrade-shepherd-services'
and co. would go through as-is, leaving users with an ugly backtrace.

* gnu/machine/ssh.scm (deploy-managed-host): Define
'eval/error-handling' and use it in lieu of EVAL as arguments to
'switch-to-system', 'upgrade-shepherd-services', and
'install-bootloader'.
</span></span></td><td>Ludovic Courtès</td></tr>