Hi,
In the GRASS building guide we tell to download a special stripped-down version of Xdr sources (with networking code removed) from the following address:
http://wiki.qgis.org/qgiswiki/BuildingWindowsBinaryOnLinux?action=AttachFile&do=get&target=xdr-4.0-mingw2.tar.gz
I think it should be better placed elsewhere (osgeo.org?)
Marco