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,
d=aa8ec684ab43fe5c348c20ea3f7a151af3eb8ffe'>diff</a></td><td class='form'><form class='right' method='get' action='/guix/log/gnu/packages/xiph.scm'>
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<div class='path'>path: <a href='/guix/log/?id=aa8ec684ab43fe5c348c20ea3f7a151af3eb8ffe'>root</a>/<a href='/guix/log/gnu?id=aa8ec684ab43fe5c348c20ea3f7a151af3eb8ffe'>gnu</a>/<a href='/guix/log/gnu/packages?id=aa8ec684ab43fe5c348c20ea3f7a151af3eb8ffe'>packages</a>/<a href='/guix/log/gnu/packages/xiph.scm?id=aa8ec684ab43fe5c348c20ea3f7a151af3eb8ffe'>xiph.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/xiph.scm?id=aa8ec684ab43fe5c348c20ea3f7a151af3eb8ffe&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2022-05-01 02:00:19 +0200'>2022-05-01</span></td><td><a href='/guix/commit/gnu/packages/xiph.scm?id=69fff28de806e3ffbb4a7a712a6871cec1182989'>gnu: libshout: Update to 2.4.6.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/xiph.scm (libshout): Update to 2.4.6.
</span></span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2021-12-30 00:52:59 -0800'>2021-12-30</span></td><td><a href='/guix/commit/gnu/packages/xiph.scm?id=4d2669ace8df1ff4ae974b63bec273412042056f'>gnu: libopusenc: Fix trailing whitespace in synopsis.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/xiph.scm (libopusenc)[synopsis]: Fix trailing whitespace.
</span></span></td><td>Vagrant Cascadian</td></tr>
<tr><td><span title='2021-12-24 16:31:03 +0100'>2021-12-24</span></td><td><a href='/guix/commit/gnu/packages/xiph.scm?id=60541df3c4ace9ce13590f9e98b0fdd9b4435c1a'>gnu: Add xiph-rnnoise.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/xiph.scm (xiph-rnnoise): New variable.
</span></span></td><td>Liliana Marie Prikler</td></tr>
<tr><td><span title='2021-12-13 22:15:07 +0100'>2021-12-13</span></td><td><a href='/guix/commit/gnu/packages/xiph.scm?id=e3196755e60ba7f1ed9d432e73f26a85e0c8893c'>gnu: Further simplify package inputs.</a><span class='msg-avail'>...<span class='msg-tooltip'>This is the result of running:

  ./pre-inst-env guix style --input-simplification=safe

and manually undoing changes on a dozen of packages to reduce
rebuilds (derivations for emacs, icecat, and libreoffice are unchanged.)
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2021-12-13 17:48:25 +0100'>2021-12-13</span></td><td><a href='/guix/commit/gnu/packages/xiph.scm?id=8394619baceb118df92e355377fd543bb1aa501a'>gnu: Simplify package inputs.</a><span class='msg-avail'>...<span class='msg-tooltip'>This commit was obtained by running:

  ./pre-inst-env guix style

without any additional argument.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2021-10-18 14:37:26 +0000'>2021-10-18</span></td><td><a href='/guix/commit/gnu/packages/xiph.scm?id=e486b2b674badc80627b11077b7df2ac1cab92d8'>Merge remote-tracking branch 'signed/master' into core-updates</a></td><td>Mathieu Othacehe</td></tr>
<tr><td><span title='2021-10-16 17:32:24 -0400'>2021-10-16</span></td><td><a href='/guix/commit/gnu/packages/xiph.scm?id=87535cbc9876295fac84c1c5be6a2ec1f72e96fb'>gnu: opusfile: Fix Opus header lookups.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/xiph.scm (opusfile)[arguments]&lt;#:phases&gt;: Add a 'fix-multistream'
phase.

Signed-off-by: Leo Famulari &lt;leo@famulari.name&gt;
</span></span></td><td>Vinicius Monego</td></tr>
<tr><td><span title='2021-07-15 10:15:26 +0300'>2021-07-15</span></td><td><a href='/guix/commit/gnu/packages/xiph.scm?id=f8e544445ffdfc4ea6fc1192e9403fb9c95f8c53'>gnu: libogg: Update to 1.3.5.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/xiph.scm (libogg): Update to 1.3.5.

Signed-off-by: Efraim Flashner &lt;efraim@flashner.co.il&gt;
</span></span></td><td>Matthew James Kraai</td></tr>