Build failure on FreeBSD with Autoconf

Looks like illegal arithmetic with time_t?

{{

{ make all-am CXX xercesc/util/XMLDateTime.lo ../../xerces-c-3.2.0/src/xercesc/util/XMLDateTime.cpp:571:27: error: invalid operands to binary expression ('time_t' (aka 'long') and 'char *(*)(int, int)') return mktime(&t) - timezone; ~~~~~~~~~~ ^ ~~~~~~~~ 1 error generated. }}

}