mklive.sh: fix issues with error handling and unmounting pseudofs

- add some error handling to `umount_pseudofs`
- disable the trap before running `error_out` to stop it running multiple times
- add `--one-file-system` to ensure that the `rm -rf` can't screw you

fixes #364

mklive.sh

@@ -52,14 +52,18 @@ mount_pseudofs() {
     done
 }
 umount_pseudofs() {
-    umount -R -f "$ROOTFS"/sys >/dev/null 2>&1
-    umount -R -f "$ROOTFS"/dev >/dev/null 2>&1
-    umount -R -f "$ROOTFS"/proc >/dev/null 2>&1
+	for f in sys dev proc; do
+		if ! umount -R -f "$ROOTFS/$f"; then
+			info_msg "ERROR: failed to unmount $ROOTFS/$f/"
+			return 1
+		fi
+	done
 }
 error_out() {
-    umount_pseudofs
-    [ -d "$BUILDDIR" -a -z "$KEEP_BUILDDIR" ] && rm -rf "$BUILDDIR"
-    exit "${1:=0}"
+	trap - INT TERM 0
+    umount_pseudofs || exit "${1:-0}"
+    [ -d "$BUILDDIR" -a -z "$KEEP_BUILDDIR" ] && rm -rf --one-file-system "$BUILDDIR"
+    exit "${1:-0}"
 }
 
 usage() {