Wow, that change has been in the Makefile for 20 years.
Here is the original bugfix:
https://github.com/chexum/genromfs/commit/6d1b1e46bb7dbc25ca521c5dfcdc37d17dca8615
The bug was:
-mkdir -p $(PREFIX)$(mandir)
+mkdir -p $(PREFIX)$(mandir)/man8
install -m 644 genromfs.8 $(PREFIX)$(mandir)/man8/
Which installed the manpage in a regular file called man8 (the use of
bindir instead of mandir was also a bug it should have done nothing).
And this one makes the code look like it does today:
https://github.com/chexum/genromfs/commit/427b121e23cd21d9b9ddb6caee3eb1064369358d
Which looks wrong to me: Why does the change use bindir? Must be some
other issue that I can't see???