package/bird: update to 2.15.1

See here for a changelog:
https://gitlab.nic.cz/labs/bird/-/blob/master/NEWS

An uClibc-ng based system needs _GNU_SOURCE in the CFLAGS to
provide getrandom().

Signed-off-by: Waldemar Brodkorb <wbx@openadk.org>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/bird/bird.hash

@@ -1,2 +1,2 @@
-sha256  3ec462a237d06d1f4455d6ec00a42f0b1686061fc988e5c89a841d01dd753b53  bird-2.0.12.tar.gz
+sha256  48e85c622de164756c132ea77ad1a8a95cc9fd0137ffd0d882746589ce75c75d  bird-2.15.1.tar.gz
 sha256  94c53c84320078920ac1f0d49c81a4e9004512f534521a58bdf145acbcbc2cd2  README

package/bird/bird.mk

@@ -4,7 +4,7 @@
 #
 ################################################################################
 
-BIRD_VERSION = 2.0.12
+BIRD_VERSION = 2.15.1
 BIRD_SITE = https://bird.network.cz/download
 BIRD_LICENSE = GPL-2.0+
 BIRD_LICENSE_FILES = README
@@ -12,6 +12,8 @@ BIRD_CPE_ID_VENDOR = nic
 BIRD_SELINUX_MODULES = bird
 BIRD_DEPENDENCIES = host-flex host-bison
 
+BIRD_CONF_ENV += CFLAGS="$(TARGET_CFLAGS) -D_GNU_SOURCE"
+
 # 0001-configure.ac-fix-build-with-autoconf-2.70.patch
 BIRD_AUTORECONF = YES