squashfs: set sensible permissions on squashfs image

target/squashfs/squashfsroot.mk

@@ -69,6 +69,7 @@ endif
 		>> $(PROJECT_BUILD_DIR)/_fakeroot.$(notdir $(SQUASHFS_TARGET))
 	chmod a+x $(PROJECT_BUILD_DIR)/_fakeroot.$(notdir $(SQUASHFS_TARGET))
 	$(STAGING_DIR)/usr/bin/fakeroot -- $(PROJECT_BUILD_DIR)/_fakeroot.$(notdir $(SQUASHFS_TARGET))
+	chmod 0644 $(SQUASHFS_TARGET)
 	-@rm -f $(PROJECT_BUILD_DIR)/_fakeroot.$(notdir $(SQUASHFS_TARGET))
 
 squashfsroot-source: squashfs-source