test-image-locking.c uses the qemu_lock_fd_test() function which is
only available on POSIX-like systems.

Message-Id: <20200804170055.2851-4-thuth@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>
Message-Id: <20200823111757.72002-4-thuth@redhat.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>