alsa-lib: update to 1.2.4

Backport upstream patch fixing compilation.

Signed-off-by: Rosen Penev <rosenp@gmail.com>

libs/alsa-lib/patches/300-snd_plugin.patch

@@ -0,0 +1,27 @@
+From ad8c8e5503980295dd8e5e54a6285d2d7e32eb1e Mon Sep 17 00:00:00 2001
+From: Jaroslav Kysela <perex@perex.cz>
+Date: Thu, 22 Oct 2020 20:57:32 +0200
+Subject: [PATCH] dlmisc: the snd_plugin_dir_set / snd_plugin_dir must be
+ declared even for \!DL_ORIGIN_AVAILABLE
+
+Fixes: 8580c081c2 ("dlsym: add support for ALSA_PLUGIN_DIR environment variable")
+BugLink: https://github.com/alsa-project/alsa-lib/issues/91
+Signed-off-by: Jaroslav Kysela <perex@perex.cz>
+---
+ src/dlmisc.c | 2 --
+ 1 file changed, 2 deletions(-)
+
+--- a/src/dlmisc.c
++++ b/src/dlmisc.c
+@@ -42,11 +42,9 @@
+ #ifndef PIC
+ struct snd_dlsym_link *snd_dlsym_start = NULL;
+ #endif
+-#ifdef DL_ORIGIN_AVAILABLE
+ static int snd_plugin_dir_set = 0;
+ static char *snd_plugin_dir = NULL;
+ #endif
+-#endif
+ 
+ #if defined(DL_ORIGIN_AVAILABLE) && defined(HAVE_LIBPTHREAD)
+ static pthread_mutex_t snd_dlpath_mutex = PTHREAD_MUTEX_INITIALIZER;