package/libsndfile: fix libsndfile.pc

Fix the following build failure with libsamplerate or minimodem raised
since bump to version 1.1.0 in commit
c59a9d12b7805f2ac08be81fe18a4ebc197d5cd9:

powerpc-buildroot-linux-uclibc-gcc.br_real: error: EXTERNAL_MPEG_LIBS@: No such file or directory

Add host-pkgconf dependency to avoid the following build failure when
running autoreconf:

configure.ac:345: error: macro PKG_INSTALLDIR is not defined; is a m4 file missing?
m4/ax_require_defined.m4:35: AX_REQUIRE_DEFINED is expanded from...

Fixes:
 - http://autobuild.buildroot.org/results/6de2d7634b1958693b7cf96fbcc79121f92347e9
 - http://autobuild.buildroot.org/results/bf66b19cacd6394957f534035af647ddd8037d60

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

package/libsndfile/0001-configure-ac-substitute-EXTERNAL_MPEG_LIBS-in-sndfile-pc.patch

@@ -0,0 +1,24 @@
+From e4fdaeefddd39bae1db27d48ccb7db7733e0c009 Mon Sep 17 00:00:00 2001
+From: Michael Cho <cho-m@tuta.io>
+Date: Sun, 17 Apr 2022 21:31:07 -0700
+Subject: [PATCH] configure.ac: substitute EXTERNAL_MPEG_LIBS in sndfile.pc
+
+[Retrieved from:
+https://github.com/libsndfile/libsndfile/commit/e4fdaeefddd39bae1db27d48ccb7db7733e0c009]
+Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
+---
+ configure.ac | 1 +
+ 1 file changed, 1 insertion(+)
+
+diff --git a/configure.ac b/configure.ac
+index 727b67bc0..a4c776d70 100644
+--- a/configure.ac
++++ b/configure.ac
+@@ -739,6 +739,7 @@ AC_SUBST(SNDIO_LIBS)
+ AC_SUBST(EXTERNAL_XIPH_CFLAGS)
+ AC_SUBST(EXTERNAL_XIPH_LIBS)
+ AC_SUBST(EXTERNAL_XIPH_REQUIRE)
++AC_SUBST(EXTERNAL_MPEG_LIBS)
+ AC_SUBST(EXTERNAL_MPEG_REQUIRE)
+ AC_SUBST(MPG123_CFLAGS)
+ AC_SUBST(MPG123_LIBS)

package/libsndfile/libsndfile.mk

@@ -11,6 +11,9 @@ LIBSNDFILE_INSTALL_STAGING = YES
 LIBSNDFILE_LICENSE = LGPL-2.1+
 LIBSNDFILE_LICENSE_FILES = COPYING
 LIBSNDFILE_CPE_ID_VENDOR = libsndfile_project
+# We're patching configure.ac
+LIBSNDFILE_AUTORECONF = YES
+LIBSNDFILE_DEPENDENCIES = host-pkgconf
 
 LIBSNDFILE_CONF_ENV = ac_cv_prog_cc_c99='-std=gnu99'
 LIBSNDFILE_CONF_OPTS = \