On systems where gnutls uses libgcrypt, I'm seeing the following
build failure

libvirt.c:314: error: variable 'virTLSThreadImpl' has initializer but incomplete type
libvirt.c:319: error: 'GCRY_THREAD_OPTION_PTHREAD' undeclared here (not in a function)
...

Fix by undefining WITH_GNUTLS_GCRYPT in config-post.h

The libvirt.so library has far too many library deps to allow
linking against it from setuid programs. Those libraries can
do stuff in __attribute__((constructor) functions which is
not setuid safe.

The virt-login-shell needs to link directly against individual
files that it uses, with all library deps turned off except
for libxml2 and libselinux.

Create a libvirt-setuid-rpc-client.la library which is linked
to by virt-login-shell. A config-post.h file allows this library
to disable all external deps except libselinux and libxml2.
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>
(cherry picked from commit 3e2f27e1)