libtirpc's version of xdr_float.c checks for __arm32__, which is a preprocessor symbol defined on NetBSD/arm. A Linux/ARM-targeted gcc will not define __arm32__, but will define __arm__ instead. Adding a " || defined(__arm__)" to xdr_float.c in the obvious place makes libtirpc build on ARM, and allows building the libtirpc rawhide srpm on the Fedora ARM port without further modifications. Please considering adding a check for __arm__.
Fixed in libtirpc-0.1.7-13.fc8 and libtirpc-0.1.7-13.fc9
libtirpc-0.1.7-13.fc8 has been pushed to the Fedora 8 stable repository. If problems still persist, please make note of it in this bug report.