systemd: enable selinux if libselinux is enabled

systemd currently has selinux disabled unconditionally.  This prevents
/sys/fs/selinux from being mounted automatically at boot which causes
audit to no longer function. This patch fixes the problem by checking if
libselinux is enabled and enabling support for selinux in systemd if so.

Signed-off-by: Adam Duskett <Adamduskett@outlook.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/systemd/systemd.mk

@@ -30,7 +30,6 @@ SYSTEMD_CONF_OPTS += \
 	--enable-blkid \
 	--enable-static=no \
 	--disable-manpages \
-	--disable-selinux \
 	--disable-pam \
 	--disable-ima \
 	--disable-libcryptsetup \
@@ -153,6 +152,13 @@ else
 SYSTEMD_CONF_OPTS += --disable-microhttpd --disable-qrencode
 endif
 
+ifeq ($(BR2_PACKAGE_LIBSELINUX),y)
+SYSTEMD_DEPENDENCIES += libselinux
+SYSTEMD_CONF_OPTS += --enable-selinux
+else
+SYSTEMD_CONF_OPTS += --disable-selinux
+endif
+
 ifeq ($(BR2_PACKAGE_SYSTEMD_HWDB),y)
 SYSTEMD_CONF_OPTS += --enable-hwdb
 else