Default APR sizes of size_t and ssize_t when cross compiling (Apache Users)

I am cross-compiling Apache HTTPD 2.2.3 on a Red Hat Linux 9 (the build machine) for a PowerPC 82xx embedded device. When I run the top-level configure script which runs among others the APR configure script, I notice that the sizeof size_t and ssize_t are being defaulted to "8" because the $cross_compiling variable is set to "yes". The same behaviour can be seen for other configure tests also: if the $cross_compiling variable is set (it is being set in the beginning because the BUILD and HOST options have been specified on the configure command-line), then various ac_cv_* variables get some default values (which in my case are not appropriate for the target HOST architecture of ppc_82xx) instead of running the cross-compiler to calculate the value.

Is this done on purpose? If so why? And how should I proceed if I want the configure script to correctly "conftest" all the needed values for my target HOST architecture? I've been searching in vain so far in FAQs, bug databases and the goonet, but I found no one with a similar problem (and a solution).