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=97256395df705dd9f9c76d18a302cbce8f94bcfe'>root</a>/<a href='/guix/log/build-aux?id=97256395df705dd9f9c76d18a302cbce8f94bcfe'>build-aux</a>/<a href='/guix/log/build-aux/build-self.scm?id=97256395df705dd9f9c76d18a302cbce8f94bcfe'>build-self.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/build-aux/build-self.scm?id=97256395df705dd9f9c76d18a302cbce8f94bcfe&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2024-07-18 11:18:29 +0100'>2024-07-18</span></td><td><a href='/guix/commit/build-aux/build-self.scm?id=d82ac48b076dca156319c16e78acfadab52fd3e5'>guix: channels: Enable specifiying available builtin builders.</a><span class='msg-avail'>...<span class='msg-tooltip'>When computing channel instance derivations.

This is useful when you want to generate compatible derivations that can be
run with a daemon that potentially doesn't support builtin builders that the
daemon you're using to generate the derivations has.

I'm looking at this in particular because I want to use this in the data
service, since it provides substitutes for derivations, and since these can be
built on other machines, it's useful to control which builtin builders they
depend on.

Fixes: &lt;https://issues.guix.gnu.org/67250&gt;.

* build-aux/build-self.scm (build-program): Accept
 #:built-in-builders and pass along to port-&gt;connection or
open-connection as approriate.
(build): Accept and pass on #:built-in-builders.
* guix/channels.scm (build-from-source, build-channel-instance,
channel-instance-derivations, channel-instances-&gt;manifest,
channel-instances-&gt;derivation): Accept and pass on
 #:built-in-builders.

Change-Id: I315c990de66c6f7dca25a859165a5568abe385ea
</span></span></td><td>Christopher Baines</td></tr>
<tr><td><span title='2021-11-27 00:49:53 +0100'>2021-11-27</span></td><td><a href='/guix/commit/build-aux/build-self.scm?id=5c1ba739d432397e7107021fd6cb3ec01aecfb64'>build-self: Help users to submit useful bug reports.</a><span class='msg-avail'>...<span class='msg-tooltip'>* build-aux/build-self.scm (build): Request the ‘COMPLETE output’.
</span></span></td><td>Tobias Geerinckx-Rice</td></tr>