xbps-src: improved xbps-src-chroot-capumount helper.

New security enhancements have been made and now you can only umount
a filesystem when the status file ".<mntpnt>_mount_bind_done" is
available in the specified masterdir.

The arguments have been changed and now it accepts two for
<masterdir> and <dir>.

xbps-src/libexec/xbps-src-chroot-helper.sh.in

@@ -95,7 +95,7 @@ umount_chroot_fs()
 		else
 			echo -n "=> Unmounting ${fs} from chroot... "
 			@@XBPS_INSTALL_LIBEXECDIR@@/xbps-src-chroot-capumount \
-				${XBPS_MASTERDIR}/${fs} 2>/dev/null
+				${XBPS_MASTERDIR} ${fs} 2>/dev/null
 			if [ $? -eq 0 ]; then
 				rm -f ${XBPS_MASTERDIR}/.${fs}_mount_bind_done
 				echo "done."