configure: fixes indent of $meson setup

convert these line from tab to space

Signed-off-by: Yonggang Luo <luoyonggang@gmail.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20201012234348.1427-2-luoyonggang@gmail.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>