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
d5d64787beb9256'>root</a>/<a href='/guix/log/gnu?id=85ba5e9335207beef9a650e96d5d64787beb9256'>gnu</a>/<a href='/guix/log/gnu/packages?id=85ba5e9335207beef9a650e96d5d64787beb9256'>packages</a>/<a href='/guix/log/gnu/packages/antivirus.scm?id=85ba5e9335207beef9a650e96d5d64787beb9256'>antivirus.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/packages/antivirus.scm?id=85ba5e9335207beef9a650e96d5d64787beb9256&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2020-10-03 23:00:21 +0200'>2020-10-03</span></td><td><a href='/guix/commit/gnu/packages/antivirus.scm?id=b7210a3241cccb80ff9056ed0c087a3bef4b0327'>gnu: clamav: Update to 0.103.0.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/antivirus.scm (clamav): Update to 0.103.0.
* gnu/packages/patches/clamav-system-tomsfastmath.patch: Update patch.
</span></span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2020-07-19 02:19:30 +0200'>2020-07-19</span></td><td><a href='/guix/commit/gnu/packages/antivirus.scm?id=7ffec020aec9ccbc531d24e65acd93e9f3962f9f'>gnu: clamav: Update to 0.102.4.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/antivirus.scm (clamav): Update to 0.102.4.
</span></span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2020-05-15 20:35:57 +0200'>2020-05-15</span></td><td><a href='/guix/commit/gnu/packages/antivirus.scm?id=6e9ffc3f778b43aa42c2142ec9ebbe3be4bf47cc'>gnu: clamav: End snippet in truth.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/antivirus.scm (clamav)[source]: Return #t from snippet.
</span></span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2020-05-15 20:35:57 +0200'>2020-05-15</span></td><td><a href='/guix/commit/gnu/packages/antivirus.scm?id=d2e438d3e2fb7ba24213dccd7ee04a9dbbca96c3'>gnu: clamav: Update to 0.102.3.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/antivirus.scm (clamav): Update to 0.102.3.
</span></span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2020-02-10 23:36:28 -0600'>2020-02-10</span></td><td><a href='/guix/commit/gnu/packages/antivirus.scm?id=a89ea0b34de0ca76cf1d1e15161b5246151ce60e'>gnu: clamav: Update to 0.102.2.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/antivirus.scm (clamav): Update to 0.102.2.
[native-inputs]: Use latest check package.
</span></span></td><td>Eric Bavier</td></tr>
<tr><td><span title='2020-02-10 23:08:54 -0600'>2020-02-10</span></td><td><a href='/guix/commit/gnu/packages/antivirus.scm?id=0e77a62dc2aad41c67feeb86c964571051107f7b'>gnu: check: Use check@0.12.</a><span class='msg-avail'>...<span class='msg-tooltip'>Tests fail to compile with check@0.13.

* gnu/packages/check.scm (clamav)[native-inputs]: 'check' -&gt; 'check-0.12'.
</span></span></td><td>Eric Bavier</td></tr>