package/frr: add libxcrypt optional dependency

Fix the following build failure raised since bump of glibc to version
2.39 in commit b5680f53d60acf8ff6010082f873438a39bd5d97:

/home/autobuild/autobuild/instance-1/output-1/per-package/frr/host/bin/../lib/gcc/i686-buildroot-linux-gnu/12.3.0/../../../../i686-buildroot-linux-gnu/bin/ld: lib/.libs/libfrr.so: undefined reference to `crypt'

Fixes: b5680f53d60acf8ff6010082f873438a39bd5d97
 - http://autobuild.buildroot.org/results/668da3829cacbe883e6cf97ce6191a8180441db6

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>

package/frr/Config.in

@@ -6,6 +6,7 @@ config BR2_PACKAGE_FRR
 	depends on BR2_TOOLCHAIN_HAS_SYNC_4 # json-c, libyang
 	select BR2_PACKAGE_BASH
 	select BR2_PACKAGE_BUSYBOX_SHOW_OTHERS # bash
+	select BR2_PACKAGE_LIBXCRYPT if BR2_TOOLCHAIN_USES_GLIBC
 	select BR2_PACKAGE_LIBYANG
 	select BR2_PACKAGE_READLINE
 	select BR2_PACKAGE_JSON_C

package/frr/frr.mk

@@ -13,7 +13,8 @@ FRR_CPE_ID_PRODUCT = free_range_routing
 FRR_AUTORECONF = YES
 
 FRR_DEPENDENCIES = host-frr readline json-c libyang \
-	$(if $(BR2_PACKAGE_C_ARES),c-ares)
+	$(if $(BR2_PACKAGE_C_ARES),c-ares) \
+	$(if $(BR2_PACKAGE_LIBXCRYPT),libxcrypt)
 
 HOST_FRR_DEPENDENCIES = host-flex host-bison host-elfutils host-python3