package/sysrepo: link with libatomic when needed

On some architectures, atomic binutils are provided by the libatomic
library from gcc. Linking with libatomic is therefore necessary,
otherwise the build fails with:

/home/buildroot/autobuild/instance-2/output-1/host/opt/ext-toolchain/bin/../lib/gcc/sparc-buildroot-linux-uclibc/7.4.0/../../../../sparc-buildroot-linux-uclibc/bin/ld: libsysrepo.so.0.7.8: undefined reference to `__atomic_fetch_add_4'

This is often for example the case on sparcv8 32 bit.

Fixes:
 - http://autobuild.buildroot.org/results/d807f3dc922a61e099a66de3bc340c018a86e150

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

package/sysrepo/sysrepo.mk

@@ -29,6 +29,10 @@ SYSREPO_CONF_OPTS = \
 # build .. https://github.com/sysrepo/sysrepo/issues/947
 SYSREPO_CONF_OPTS += -DUSE_SR_MEM_MGMT=OFF
 
+ifeq ($(BR2_TOOLCHAIN_HAS_LIBATOMIC),y)
+SYSREPO_CONF_OPTS += -DCMAKE_EXE_LINKER_FLAGS=-latomic
+endif
+
 define SYSREPO_INSTALL_INIT_SYSV
 	$(INSTALL) -m 755 -D package/sysrepo/S50sysrepod \
 		$(TARGET_DIR)/etc/init.d/S50sysrepod