rpm spec: disable ceph on 32-bit architectures

Ceph in upstream and Fedora has dropped support for building on host
architectures which are 32-bit.
Signed-off-by: NDaniel P. Berrangé <berrange@redhat.com>

libvirt.spec.in

@@ -109,6 +109,12 @@
     %define with_storage_zfs 0
 %endif
 
+# Ceph dropping support for 32-bit hosts
+%if 0%{fedora} >= 30
+    %ifarch %{arm} %{ix86}
+        %define with_storage_rbd 0
+    %endif
+%endif
 
 # RHEL doesn't ship OpenVZ, VBox, PowerHypervisor,
 # VMware, libxenserver (xenapi), libxenlight (Xen 4.1 and newer),