unifdef(1) on OpenBSD
The text 40b85af33b3f, as OpenBSD 7.3, OpenBSD 7.2, OpenBSD 7.1 shipped it.
remove preprocessor conditionals from code
Flags it lists
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-B -
-K -
-M -
-S -
-U -
-V -
-b -
-c -
-d -
-e -
-f -
-h -
-iU -
-k -
-m -
-n -
-o -
-s -
-t