Borrowed from Debian
https://sources.debian.org/src/gnupg1/1.4.23-1.1/debian/patches/0006-fix-for-gcc10.patch/

Subject: Fix build with gcc-10
Author: Christoph Biedl <debian.axhn@manchmal.in-ulm.de>
Date: 2021-01-04
Bug: https://dev.gnupg.org/T5215
Bug-Debian: https://bugs.debian.org/957293

--- a/g10/options.h
+++ b/g10/options.h
@@ -29,6 +29,8 @@
 /* Norcraft can't cope with common symbols */
 #if defined (__riscos__) && !defined (INCLUDED_BY_MAIN_MODULE)
 #define EXTERN_UNLESS_MAIN_MODULE extern
+#elif defined (__GNUC__) && __GNUC__ >= 10
+#define EXTERN_UNLESS_MAIN_MODULE __attribute__((__common__))
 #else
 #define EXTERN_UNLESS_MAIN_MODULE
 #endif
--- a/include/cipher.h
+++ b/include/cipher.h
@@ -117,6 +117,8 @@
 #ifndef EXTERN_UNLESS_MAIN_MODULE
 #if defined (__riscos__) && !defined (INCLUDED_BY_MAIN_MODULE)
 #define EXTERN_UNLESS_MAIN_MODULE extern
+#elif defined (__GNUC__) && __GNUC__ >= 10
+#define EXTERN_UNLESS_MAIN_MODULE __attribute__((__common__))
 #else
 #define EXTERN_UNLESS_MAIN_MODULE
 #endif
--- a/include/iobuf.h
+++ b/include/iobuf.h
@@ -72,6 +72,8 @@
 #ifndef EXTERN_UNLESS_MAIN_MODULE
 #if defined (__riscos__) && !defined (INCLUDED_BY_MAIN_MODULE)
 #define EXTERN_UNLESS_MAIN_MODULE extern
+#elif defined (__GNUC__) && __GNUC__ >= 10
+#define EXTERN_UNLESS_MAIN_MODULE __attribute__((__common__))
 #else
 #define EXTERN_UNLESS_MAIN_MODULE 
 #endif
--- a/include/memory.h
+++ b/include/memory.h
@@ -93,6 +93,8 @@
 #ifndef EXTERN_UNLESS_MAIN_MODULE
 #if defined (__riscos__) && !defined (INCLUDED_BY_MAIN_MODULE)
 #define EXTERN_UNLESS_MAIN_MODULE extern
+#elif defined (__GNUC__) && __GNUC__ >= 10
+#define EXTERN_UNLESS_MAIN_MODULE __attribute__((__common__))
 #else
 #define EXTERN_UNLESS_MAIN_MODULE 
 #endif
--- a/include/mpi.h
+++ b/include/mpi.h
@@ -38,6 +38,8 @@
 #ifndef EXTERN_UNLESS_MAIN_MODULE
 #if defined (__riscos__) && !defined (INCLUDED_BY_MAIN_MODULE)
 #define EXTERN_UNLESS_MAIN_MODULE extern
+#elif defined (__GNUC__) && __GNUC__ >= 10
+#define EXTERN_UNLESS_MAIN_MODULE __attribute__((__common__))
 #else
 #define EXTERN_UNLESS_MAIN_MODULE 
 #endif
 href='/guix/log/gnu?id=ebeb018ca32c3da0dc820440b2da8d229f78946b'>gnu</a>/<a href='/guix/log/gnu/services?id=ebeb018ca32c3da0dc820440b2da8d229f78946b'>services</a>/<a href='/guix/log/gnu/services/rsync.scm?id=ebeb018ca32c3da0dc820440b2da8d229f78946b'>rsync.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/services/rsync.scm?id=ebeb018ca32c3da0dc820440b2da8d229f78946b&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2019-03-04 15:22:58 +0100'>2019-03-04</span></td><td><a href='/guix/commit/gnu/services/rsync.scm?id=56a93cb975ddc33d50183fb122e2aafda026f18e'>services: Use 'file-append' for user account shells.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/services/cuirass.scm (cuirass-account): Use 'file-append' instead
of #~(string-append #$shadow "/sbin/nologin").
* gnu/services/monitoring.scm (zabbix-server-account): Likewise.
(zabbix-agent-account): Likewise.
* gnu/services/rsync.scm (rsync-account): Likewise.
* gnu/services/ssh.scm (%openssh-accounts): Likewise.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2017-09-23 21:07:27 +0100'>2017-09-23</span></td><td><a href='/guix/commit/gnu/services/rsync.scm?id=9db7e9be59820190a97de22ba72e71fa25f9d168'>gnu: Add rsync service.</a><span class='msg-avail'>...<span class='msg-tooltip'>* doc/guix.texi (Networking Services): Add rsync service documentation.
* gnu/services/rsync.scm (&lt;rsync-configuration&gt;): New file.
* gnu/tests/rsync.scm: New file.
* gnu/local.mk (GNU_SYSTEM_MODULES): Add new files.

Signed-off-by: Christopher Baines &lt;mail@cbaines.net&gt;
</span></span></td><td>Oleg Pykhalov</td></tr>