Fixes 'multiple definition errors' when building with GCC 10+

From: https://bugs.gentoo.org/710796
Originally from: https://gitlab.freedesktop.org/pipewire/pipewire/-/commit/a62e41e
and https://gitlab.freedesktop.org/pipewire/pipewire/-/commit/7a976c7

--- a/spa/plugins/bluez5/a2dp-codecs.h
+++ b/spa/plugins/bluez5/a2dp-codecs.h
@@ -284,15 +284,15 @@
         }
 }
 
-const a2dp_sbc_t bluez_a2dp_sbc;
+extern const a2dp_sbc_t bluez_a2dp_sbc;
 #if ENABLE_MP3
-const a2dp_mpeg_t bluez_a2dp_mpeg;
+extern const a2dp_mpeg_t bluez_a2dp_mpeg;
 #endif
 #if ENABLE_AAC
-const a2dp_aac_t bluez_a2dp_aac;
+extern const a2dp_aac_t bluez_a2dp_aac;
 #endif
 #if ENABLE_APTX
-const a2dp_aptx_t bluez_a2dp_aptx;
+extern const a2dp_aptx_t bluez_a2dp_aptx;
 #endif
 
 #endif
--- a/spa/plugins/bluez5/bluez5-monitor.c
+++ b/spa/plugins/bluez5/bluez5-monitor.c
@@ -75,7 +75,7 @@
 	struct spa_list transport_list;
 };
 
-struct spa_handle_factory spa_a2dp_sink_factory;
+extern struct spa_handle_factory spa_a2dp_sink_factory;
 
 static void fill_item(struct spa_bt_monitor *this, struct spa_bt_transport *transport,
 		struct spa_pod **result, struct spa_pod_builder *builder)
--- a/spa/plugins/bluez5/meson.build
+++ b/spa/plugins/bluez5/meson.build
@@ -1,7 +1,8 @@
 
 bluez5_sources = ['plugin.c',
 		  'a2dp-sink.c',
-                  'bluez5-monitor.c']
+		  'a2dp-codecs.c',
+		  'bluez5-monitor.c']
 
 bluez5lib = shared_library('spa-bluez5',
 	bluez5_sources,
b89addc9ab25b5e488c443575'>commit</a><a href='/guix/diff/gnu/tests/data/jami-dummy-account.dat?id=802307fe6f6ce5cb89addc9ab25b5e488c443575'>diff</a></td><td class='form'><form class='right' method='get' action='/guix/log/gnu/tests/data/jami-dummy-account.dat'>
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<div class='path'>path: <a href='/guix/log/?id=802307fe6f6ce5cb89addc9ab25b5e488c443575'>root</a>/<a href='/guix/log/gnu?id=802307fe6f6ce5cb89addc9ab25b5e488c443575'>gnu</a>/<a href='/guix/log/gnu/tests?id=802307fe6f6ce5cb89addc9ab25b5e488c443575'>tests</a>/<a href='/guix/log/gnu/tests/data?id=802307fe6f6ce5cb89addc9ab25b5e488c443575'>data</a>/<a href='/guix/log/gnu/tests/data/jami-dummy-account.dat?id=802307fe6f6ce5cb89addc9ab25b5e488c443575'>jami-dummy-account.dat</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/tests/data/jami-dummy-account.dat?id=802307fe6f6ce5cb89addc9ab25b5e488c443575&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2021-08-02 17:23:30 -0400'>2021-08-02</span></td><td><a href='/guix/commit/gnu/tests/data/jami-dummy-account.dat?id=10f554700c417b84c22c56fdd007567a52c45d75'>Reinstate "services: Add a service for Jami."</a><span class='msg-avail'>...<span class='msg-tooltip'>This reverts commit 4673f817938d9d2b1b40a072ab2e0c44a32ccc97, which reverted
commit 69dcc24c9f0cdfea674eb690e7755d26a25ced2b with the fix detailed below.

Thanks to Christopher Baines for reporting the failure and proposing a fix.

* guix/self.scm (compiled-guix) [*system-test-modules*]: Add the test data
files via the 'extra-files' argument.
* gnu/local.mk (dist_patch_DATA): Move the tests/data/jami-dummy-account.dat
file to...
* gnu/local.mk (MODULES_NOT_COMPILED): ... here.
</span></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/gnu/tests/data/jami-dummy-account.dat?id=4673f817938d9d2b1b40a072ab2e0c44a32ccc97'>Revert "services: Add a service for Jami."</a><span class='msg-avail'>...<span class='msg-tooltip'>This reverts commit 69dcc24c9f0cdfea674eb690e7755d26a25ced2b.  It broke 'guix
pull'.
</span></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/gnu/tests/data/jami-dummy-account.dat?id=69dcc24c9f0cdfea674eb690e7755d26a25ced2b'>services: Add a service for Jami.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/services/telephony.scm (string-or-computed-file?)
(string-list?, account-fingerprint-list?): New procedures.
(maybe-string-list, maybe-account-fingerprint-list)
(maybe-boolean, maybe-string, jami-account-list): New configuration field
types.
(serialize-string-list, serialize-boolean, serialize-string)
(jami-account, jami-account-&gt;alist, jami-configuration)
(jami-account-list?, jami-account-list-maybe): New procedures.
(%jami-accounts): New variable.
(jami-configuration-&gt;command-line-arguments): New procedure.
(jami-dbus-session-activation, jami-shepherd-services): New procedures.
(jami-service-type): New variable.
* gnu/build/jami-service.scm: New file.
* gnu/tests/data/jami-dummy-account.dat: Likewise.
* gnu/tests/telephony.scm: Likewise.
* gnu/local.mk (GNU_SYSTEM_MODULES): Register them.
* Makefile.am (SCM_TESTS): Register the test file.
(dist_patch_DATA): Register the new data file.
* doc/guix.texi (Telephony Services): Document it.
</span></span></td><td>Maxim Cournoyer</td></tr>