package/alsa-lib: fix static build

Fix the following build failure raised since bump to version 1.2.5.1 in
commit af19131543926879fb6676a3352c63ac0b2038bc:

/home/buildroot/autobuild/run/instance-0/output-1/host/opt/ext-toolchain/bin/../lib/gcc/arm-buildroot-linux-uclibcgnueabi/9.3.0/../../../../arm-buildroot-linux-uclibcgnueabi/bin/ld: ../src/.libs/libasound.a(control_symbols.o):(.data+0x4): undefined reference to `_snd_module_control_empty'

Fixes:
 - http://autobuild.buildroot.org/results/a8fd791ba4c289cc4fc744a8ff9615bacd9558f3

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/alsa-lib/0003-control-empty-fix-the-static-build.patch

@@ -0,0 +1,29 @@
+From 81e7923fbfad45b2f353a4d6e3053af51f5f7d0b Mon Sep 17 00:00:00 2001
+From: Jaroslav Kysela <perex@perex.cz>
+Date: Tue, 15 Jun 2021 23:21:42 +0200
+Subject: [PATCH] control: empty - fix the static build
+
+Reported-by: Jan Palus <atler@pld-linux.org>
+Fixes: https://github.com/alsa-project/alsa-lib/issues/157
+Signed-off-by: Jaroslav Kysela <perex@perex.cz>
+
+[Retrieved from:
+https://github.com/alsa-project/alsa-lib/commit/81e7923fbfad45b2f353a4d6e3053af51f5f7d0b]
+Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
+---
+ src/control/control_empty.c | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/src/control/control_empty.c b/src/control/control_empty.c
+index 49d1026c..c9b048c1 100644
+--- a/src/control/control_empty.c
++++ b/src/control/control_empty.c
+@@ -30,7 +30,7 @@
+ 
+ #ifndef PIC
+ /* entry for static linking */
+-const char *_snd_module_ctl_empty = "";
++const char *_snd_module_control_empty = "";
+ #endif
+ 
+ /*! \page control_plugins