lh_binary_rootfs: Remove

mksquashfs has a nasty habit of segfaulting when creating an image where
an image already exists. This can happen, for example, if you are
performing multiple runs of lh_binary and the build breaks for some reason.

This is almost certainly a bug in mksquashfs; I will look into finding a
suitable testcase.

helpers/lh_binary_rootfs

@@ -215,6 +215,9 @@ case "${LH_CHROOT_FILESYSTEM}" in
 			rm -f binary/${INITFS}/filesystem.squashfs
 		fi
 
+		# Remove stale squashfs image
+		rm -f chroot/filesystem.squashfs
+
 		if [ "${LH_QUIET}" = "enabled" ] && [ "${LH_DISTRIBUTION}" != "etch" ] && [ "${LH_DISTRIBUTION}" != "testing" ]
 		then
 			MKSQUASHFS_OPTIONS="${MKSQUASHFS_OPTIONS} -no-progress"