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=09535959a9d17f0d327f3454dc78c0be1f7b43e4'>root</a>/<a href='/guix/log/tests?id=09535959a9d17f0d327f3454dc78c0be1f7b43e4'>tests</a>/<a href='/guix/log/tests/services?id=09535959a9d17f0d327f3454dc78c0be1f7b43e4'>services</a>/<a href='/guix/log/tests/services/telephony.scm?id=09535959a9d17f0d327f3454dc78c0be1f7b43e4'>telephony.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/tests/services/telephony.scm?id=09535959a9d17f0d327f3454dc78c0be1f7b43e4&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2022-07-07 10:43:08 -0400'>2022-07-07</span></td><td><a href='/guix/commit/tests/services/telephony.scm?id=258bc4c4e668e9817471d04d052bc0a8e2d43fa0'>tests: telephony: Remove obsolete parsing tests.</a><span class='msg-avail'>...</span></td><td>Maxim Cournoyer</td></tr>
<tr><td><span title='2021-08-02 17:23:30 -0400'>2021-08-02</span></td><td><a href='/guix/commit/tests/services/telephony.scm?id=10f554700c417b84c22c56fdd007567a52c45d75'>Reinstate "services: Add a service for Jami."</a><span class='msg-avail'>...</span></td><td>Maxim Cournoyer</td></tr>
<tr><td><span title='2021-08-02 15:48:59 -0400'>2021-08-02</span></td><td><a href='/guix/commit/tests/services/telephony.scm?id=4673f817938d9d2b1b40a072ab2e0c44a32ccc97'>Revert "services: Add a service for Jami."</a><span class='msg-avail'>...</span></td><td>Maxim Cournoyer</td></tr>
<tr><td><span title='2021-08-02 15:15:02 -0400'>2021-08-02</span></td><td><a href='/guix/commit/tests/services/telephony.scm?id=69dcc24c9f0cdfea674eb690e7755d26a25ced2b'>services: Add a service for Jami.</a><span class='msg-avail'>...</span></td><td>Maxim Cournoyer</td></tr>