Set PKG_CONFIG_PATH correctly wrt target arch.
Optimally belongs in redhat-rpm-config but easier to just add here...

--- rpm-4.4.2/macros.in.pkgconfigpath	2007-01-30 15:57:37.000000000 -0500
+++ rpm-4.4.2/macros.in	2007-01-30 16:04:25.000000000 -0500
@@ -926,6 +926,8 @@
   export RPM_BUILD_ROOT}\
   %{?_javaclasspath:CLASSPATH=\"%{_javaclasspath}\"\
   export CLASSPATH}\
+  PKG_CONFIG_PATH=\"%{_libdir}/pkgconfig:%{_datadir}/pkgconfig\"\
+  export PKG_CONFIG_PATH\
   \
   %{verbose:set -x}%{!verbose:exec > /dev/null}\
   umask 022\