The gc test does not link to the libgcrypt library, consequently the build breaks. To have this link, add gc_LDADD = $(LDADD) $(LIBGCRYPT_LIBS) to tests/Makefile.am.
firstname.lastname@example.org has created a patch for this and sent it upstream.
patch applied to gnutls-1.2.10-r1
Also added with patch gnutls-1.2.11 and gnutls-1.4.1 (package masked until further testing done).
Thanks for the bug report.
Fixed upstream on 1.2, 1,4, and 1.5 branches according to Simon Josefsson. Verified in CVS logs at http://cvs.gnupg.org/cgi-bin/viewcvs.cgi/gnutls/tests/Makefile.am?rev=1.37&root=GNU+TLS+Library&view=log