Perhaps you have a 3rd party Apache installed as your webserver, or you had a 3rd party Apache installed somewhere in your path that apxs is finding.
If you have a 3rd party apache installed, try changing the configure to
--with-apxs=<path to apxs>
or if it is an Apache 2 compile
--with-apxs2=<path to apxs2>
where <path to apxs(2)> is the path to the 3rd party apache.
When you make install, php should replace the apxs module that used to be there.
If you had some apxs that it is using (the wrong one), you can force it to use the Mac OS X bundled one with
tychay at php dot net