Eventually, I managed to get mod_fastcgi to compile on FreeBSD. See PR#91190. It basically amounted to applying the patch in the mailing list automatically. But what really surprised me were the changes to the port’s Makefile. I trimmed out about 50 lines of confusion into this:
AP_FAST_BUILD= yes AP_GENPLIST= yes SRC_FILE= *.c PORTDOCS= LICENSE.TERMS mod_fastcgi.html
This is all thanks to the new bsd.apache.mk support. It really works well. However, it is slightly underdocumented. But this isn’t much of a problem.
less /usr/ports/www/mod_*/Makefile provided enough hints to get going quickly.
Now I just need to get the maintainer approval, in order to get this committed…