tests: Add dependency on screenshooter client protocol

Given that the test-helper code relies on the screenshooter protocol,
make sure it's available for us to build, and the dependency ensures we
build in order.

Fixes: #588

Signed-off-by: Daniel Stone <daniels@collabora.com>

tests/meson.build

@@ -29,8 +29,9 @@ lib_test_client = static_library(
 		'weston-test-client-helper.c',
 		'weston-test-fixture-compositor.c',
 		weston_test_client_protocol_h,
-		weston_screenshooter_protocol_c,
 		weston_test_protocol_c,
+		weston_screenshooter_client_protocol_h,
+		weston_screenshooter_protocol_c,
 		viewporter_client_protocol_h,
 		viewporter_protocol_c,
 		'color_util.h',