lxc: set --with-runtime-path to the /var/run path

The default runtime directory used by LXC is /run which doesn't exist
in OpenWrt. It causes errors like:

Failed to create lock for foo
lxc-create: foo: tools/lxc_create.c: main: 260 Failed to create lxc container

There has been workaround for that in the lxc-auto.init but it requires
installing "lxc-auto" package. Replacing that "ln -s" workaround with
Makefile specifying --with-runtime-path allows using pure "lxc" in
OpenWrt (without the "lxc-auto").

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
(cherry picked from commit 90fef036fe)

utils/lxc/Makefile

@@ -144,7 +144,8 @@ CONFIGURE_ARGS += \
 	--disable-selinux \
 	--$(if $(CONFIG_LXC_SECCOMP),en,dis)able-seccomp \
 	--enable-capabilities \
-	--disable-examples
+	--disable-examples \
+	--with-runtime-path=/var/run
 
 ifdef CONFIG_USE_MIPS16
   TARGET_CFLAGS += -minterlink-mips16

utils/lxc/files/lxc-auto.init

@@ -69,9 +69,5 @@ boot() {
 		mount -t cgroup -o rw,nosuid,nodev,noexec,relatime,none,name=systemd cgroup /sys/fs/cgroup/systemd
 	fi
 
-	if [ ! -d /run ]; then
-		ln -s /var/run /run
-	fi
-
 	start
 }