We have dropped various source that is useless to use, so ignore cleaning them.

--- a/buildrump.sh/src/build.sh
+++ b/buildrump.sh/src/build.sh
@@ -2767,7 +2767,7 @@
 			;;
 
 		cleandir|obj|sourcesets|syspkgs|params|show-params)
-			${runcmd} "${makewrapper}" ${parallel} ${op} ||
+			${runcmd} "${makewrapper}" -k ${parallel} ${op} ||
 			    bomb "Failed to make ${op}"
 			statusmsg "Successful make ${op}"
 			;;
