All builtins of gl_out, like gl_out[].gl_Position need to be
considered active as well.

Bug: angleproject:5557
Test: dEQP-GLES31.functional.tessellation.shader_input_output.gl_position_tcs_to_tes
Change-Id: I74aeef86be573dc8df17472b88acd521032d7921
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2786630
Commit-Queue: Mohan Maiya <m.maiya@samsung.com>
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>