+subdirmk: warning (unknown-warning): ./Prefix.sd.mk:2: unknown warning many-requests-for-unknown-warning requested
+subdirmk: warning (single-char-var): ./Dir.sd.mk:8: possibly confusing unbracketed single-char $-expansion
+subdirmk: warning (broken-var-ref): ./Dir.sd.mk:19: broken $&... expansion; you probably meant &$
+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 ./Dir.sd.mk:7
+ saw &WARN at ./Dir.sd.mk:10
+ saw &WARN at ./Dir.sd.mk:11
+subdirmk: warning (unknown-warning): ./sub/dir/Dir.sd.mk:3: attempt to suppress unknown warning(s) `some-unknown-warning'