package/monit: fix build without SSP

Fix build without SSP raised since bump to version 5.33.0 in commit
8cedb39764f70f9d467bf0cc1acc99a8bbb963d6:

configure:10524: checking for pthread_create in -lpthread
configure:10547: /home/thomas/autobuild/instance-1/output-1/host/bin/arceb-buildroot-linux-uclibc-gcc -o conftest -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64  -Ofast -g0  -static -Wextra -fstack-protector-all -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64  -static conftest.c -lpthread   >&5
/home/thomas/autobuild/instance-1/output-1/host/lib/gcc/arceb-buildroot-linux-uclibc/10.2.0/../../../../arceb-buildroot-linux-uclibc/bin/ld: cannot find -lssp_nonshared

[...]

checking for pthread_create in -lpthread... no
configure: error: POSIX thread library is required

Fixes:
 - http://autobuild.buildroot.org/results/ce0f9f62d60f801b03a079135941424ad147cf45

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

package/monit/monit.mk

@@ -18,6 +18,7 @@ MONIT_AUTORECONF = YES
 MONIT_CONF_ENV = \
 	libmonit_cv_setjmp_available=yes \
 	libmonit_cv_vsnprintf_c99_conformant=yes \
+	ax_cv_check_cflags___fstack_protector_all=$(if $(BR2_TOOLCHAIN_HAS_SSP),yes,no) \
 	ac_cv_ipv6=yes
 
 MONIT_CONF_OPTS += \