src: only import sys/uio.h when journald is built
src: only import sys/uio.h when journald is built

The sys/uio.h header is only needed when building logging
code with journald support enabled. Conditionally include
it so that we avoid break on platforms which lack this
header.

Reviewed-by: Pavel Hrdina <d4772d05997b8abf035041e3b4f4996380ea7e7a@redhat.com>
Signed-off-by: Daniel P. Berrangé <bb938cf255e055ff3507f2627d214e8e62118fcf@redhat.com>

libvirt/libvirt,crobinso/libvirt,jardasgit/libvirt,libvirt/libvirt,crobinso/libvirt,olafhering/libvirt,olafhering/libvirt,nertpinx/libvirt,olafhering/libvirt,fabianfreyer/libvirt,jardasgit/libvirt,libvirt/libvirt,jfehlig/libvirt,fabianfreyer/libvirt,jfehlig/libvirt,fabianfreyer/libvirt,olafhering/libvirt,jardasgit/libvirt,crobinso/libvirt,libvirt/libvirt,nertpinx/libvirt,jardasgit/libvirt,fabianfreyer/libvirt,jfehlig/libvirt,crobinso/libvirt,zippy2/libvirt,nertpinx/libvirt,fabianfreyer/libvirt,nertpinx/libvirt,jardasgit/libvirt,nertpinx/libvirt,jfehlig/libvirt,zippy2/libvirt,zippy2/libvirt,zippy2/libvirt