apxs does not handle binary distributables installed at non-default locations. Specifically, apxs complains that there is no DSO support available when the real issue is that the apxs command used to check for DSO support (which is essentially "if (not grep(/mod_so/, httpd -l")) does not provide httpd with appropriate -d and -R arguments. Without this fix, binary distributables give every appearance of having unusable apxs support! For all Apache binary distributables that I build, I patch apxs.pl before building, but this is ridiculous -- this should simply be fixed in the normal source tree.
Note: This has been fixed in the Apache 2.0 stream. It's only the Apache 1.3.x stream that is broken in this respect.