build: unbreak fakeroot in SDK

Using fakeroot without passing the paths to libfakeroot.sh and faked
causes havoc. Use the $(FAKEROOT) Make variable which includes them.

Fixes: 353ce2e521 ("build: ipkg-build use fakeroot with PKG_FILE_MODES")
Signed-off-by: Daniel Golle <[email protected]>

include/image.mk

@@ -250,7 +250,7 @@ define Image/mkfs/squashfs
 	     "$(call mkfs_target_dir,$(1))" > [email protected]
 	echo "$(Image/mkfs/squashfs-common)" >> [email protected]
 	chmod +x [email protected]
-	$(STAGING_DIR_HOST)/bin/fakeroot [email protected]
+	$(FAKEROOT) "[email protected]"
 endef
 else
 define Image/mkfs/squashfs