subdirmk: warning (local+global): saw both WARN and &WARN
saw WARN at ./Dir.sd.mk:6
saw WARN at ./Dir.sd.mk:9
+ saw WARN at ./sub/dir/Dir.sd.mk:16
+ saw WARN at ./sub/dir/Dir.sd.mk:19
saw &WARN at ./Dir.sd.mk:7
saw &WARN at ./Dir.sd.mk:10
saw &WARN at ./Dir.sd.mk:11
+ saw &WARN at ./sub/dir/Dir.sd.mk:15
subdirmk: warning (unknown-warning): ./sub/dir/Dir.sd.mk:3: attempt to suppress unknown warning(s) `some-unknown-warning'