package/libodb-mysql: fix static build

Use mysql_config to help libodb-mysql to retrieve mysql dependencies
such as -lz

Fixes:
 - http://autobuild.buildroot.org/results/a5447c5105f15606ed562b39ca84c06e7e6b78c0

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

package/libodb-mysql/libodb-mysql.mk

@@ -12,5 +12,6 @@ LIBODB_MYSQL_INSTALL_STAGING = YES
 LIBODB_MYSQL_LICENSE = GPL-2.0
 LIBODB_MYSQL_LICENSE_FILES = LICENSE
 LIBODB_MYSQL_DEPENDENCIES = libodb mysql
+LIBODB_MYSQL_CONF_ENV = LIBS="$(shell $(STAGING_DIR)/usr/bin/mysql_config --libs)"
 
 $(eval $(autotools-package))