While attempting to build a (pre-)5.0 of glusterfs on Ubuntu bionic and cosmic, it became apparent that there are some gremlins hiding in the combination of the xlator export-symbols, the newish addition of -Wl,--no-undefined, and the new switch to libuuid from the old contrib/uuid. Note: even though Fedora 28 (and later) and Ubuntu bionic (and later) have the same nominal version of libtool, the Fedora version appears to do a better job of recursing through dependencies to determine the libraries to link with. Examination of the build logs showed that despite appearing to work on Fedora, not all xlators and shared libs were linked with -Wl, --no-undefined, and -luuid. And in the case of the gnfs xlator, it was not only not linked with -Wl,--no-undefined but alsos not linked with -lgfxdr and -lgfrpc. Added GF_XLATOR_LDFLAGS, similar to GF_XLATOR_DEFAULT_LDFLAGS. GF_XLATOR_DEFAULT_LDFLAGS is for xlators that export/expose the default or common set of symbols. GF_XLATOR_LDFLAGS is for those remaining xlators that export/expose non-default symbols, e.g. dht and glupy. This removes the need in the future to add things like $(UUID_LIBS) to every xlator's Makefile.am. Just add it to GF_XLATOR_LDFLAGS and GF_XLATOR_DEFAULT_LDFLAGS in configure.ac and you're done. This patch was tested on Fedora 28 (build, rpmbuild), Fedora Rawhide/30 (rpmbuild), RHEL8 (rpmbuild), CentOS7 (rpmbuild), Fedora koji --scratch build for f30/rawhide, and a Launch