fs/squashfs: honour the number of parallel jobs

By default, mksquashfs uses all the CPUs available, like us with
BR2_JLEVEL=0.

However, by setting BR21_JLEVEL to non-zero, a user volutarily limits
the number of jobbs allowed to run concurrently (for various reasons,
like this is not a priority task on the machine; or like the
autobuilders, to spread the load accross multiple runs without
overloading the machine).

So, propagate tthe parallelisn settings down to mksquashfs, to repect
the user's will.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Clayton Shotwell <clayton.shotwell@rockwellcollins.com>
Tested-by: Clayton Shotwell <clayton.shotwell@rockwellcollins.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>

fs/squashfs/squashfs.mk

@@ -6,6 +6,8 @@
 
 ROOTFS_SQUASHFS_DEPENDENCIES = host-squashfs
 
+ROOTFS_SQUASHFS_ARGS = -noappend -processors $(PARALLEL_JOBS)
+
 ifeq ($(BR2_TARGET_ROOTFS_SQUASHFS4_LZ4),y)
 ROOTFS_SQUASHFS_ARGS += -comp lz4 -Xhc
 else ifeq ($(BR2_TARGET_ROOTFS_SQUASHFS4_LZO),y)
@@ -19,8 +21,7 @@ ROOTFS_SQUASHFS_ARGS += -comp gzip
 endif
 
 define ROOTFS_SQUASHFS_CMD
-	$(HOST_DIR)/bin/mksquashfs $(TARGET_DIR) $@ -noappend \
-		$(ROOTFS_SQUASHFS_ARGS)
+	$(HOST_DIR)/bin/mksquashfs $(TARGET_DIR) $@ $(ROOTFS_SQUASHFS_ARGS)
 endef
 
 $(eval $(call ROOTFS_TARGET,squashfs))