Check losetup capabilities before specifying to mount as read-only.

This is to retain compatibility with Etch's non-loop-aes-utils' losetup.

Signed-off-by: Chris Lamb <chris@chris-lamb.co.uk>

scripts/live

@@ -1008,7 +1008,12 @@ setup_unionfs ()
 			rofslist="${image} ${rofslist}"
 		elif [ -f "${image}" ]
 		then
-			backdev=$(get_backing_device "${image}" "-r")
+			if /sbin/losetup --help 2>&1 | grep -q -- "-r\b"
+			then
+				backdev=$(get_backing_device "${image}" "-r")
+			else
+				backdev=$(get_backing_device "${image}")
+			fi
 			fstype=$(get_fstype "${backdev}")
 
 			if [ "${fstype}" = "unknown" ]

scripts/live-helpers

@@ -181,7 +181,10 @@ setup_loop ()
 
 			if [ -n ${readonly} ]
 			then
-				options="${options} -r"
+				if /sbin/losetup --help 2>&1 | grep -q -- "-r\b"
+				then
+					options="${options} -r"
+				fi
 			fi
 
 			if [ 0 -lt "${offset}" ]