spec: Build vbox packages only for x86 architectures
spec: Build vbox packages only for x86 architectures

Commit 6ab6bc19f03513fd87d29ecfd405bb7f4a7de114 has introduced separate
daemon/driver packages for vbox. These should only be built for x86
architectures which is done hereby.

Signed-off-by: Viktor Mihajlovski <a96a137ca8976b5ff3114c85be7aeb3b6464dad7@linux.vnet.ibm.com>

andreabolognani/libvirt,nertpinx/libvirt,jfehlig/libvirt,andreabolognani/libvirt,jfehlig/libvirt,VenkatDatta/libvirt,cbosdo/libvirt,datto/libvirt,olafhering/libvirt,elmarco/libvirt,olafhering/libvirt,zhlcindy/libvirt-1.1.4-maintain,fabianfreyer/libvirt,elmarco/libvirt,cbosdo/libvirt,zippy2/libvirt,libvirt/libvirt,libvirt/libvirt,andreabolognani/libvirt,rlaager/libvirt,agx/libvirt,VenkatDatta/libvirt,taget/libvirt,shugaoye/libvirt,taget/libvirt,datto/libvirt,rlaager/libvirt,VenkatDatta/libvirt,cbosdo/libvirt,zhlcindy/libvirt-1.1.4-maintain,agx/libvirt,shugaoye/libvirt,VenkatDatta/libvirt,taget/libvirt,fabianfreyer/libvirt,eskultety/libvirt,crobinso/libvirt,datto/libvirt,crobinso/libvirt,jardasgit/libvirt,elmarco/libvirt,shugaoye/libvirt,jardasgit/libvirt,fabianfreyer/libvirt,shugaoye/libvirt,zhlcindy/libvirt-1.1.4-maintain,rlaager/libvirt,zippy2/libvirt,cbosdo/libvirt,rlaager/libvirt,zhlcindy/libvirt-1.1.4-maintain,libvirt/libvirt,agx/libvirt,olafhering/libvirt,jardasgit/libvirt,agx/libvirt,elmarco/libvirt,jfehlig/libvirt,eskultety/libvirt,nertpinx/libvirt,rlaager/libvirt,datto/libvirt,andreabolognani/libvirt,jardasgit/libvirt,eskultety/libvirt,nertpinx/libvirt,olafhering/libvirt,nertpinx/libvirt,eskultety/libvirt,taget/libvirt,datto/libvirt,zippy2/libvirt,taget/libvirt,elmarco/libvirt,jfehlig/libvirt,andreabolognani/libvirt,fabianfreyer/libvirt,zhlcindy/libvirt-1.1.4-maintain,jardasgit/libvirt,VenkatDatta/libvirt,eskultety/libvirt,nertpinx/libvirt,cbosdo/libvirt,fabianfreyer/libvirt,libvirt/libvirt,crobinso/libvirt,agx/libvirt,shugaoye/libvirt,zippy2/libvirt,crobinso/libvirt