Enable cube map arrays on SwiftShader. Bug: angleproject:5142 Change-Id: I51c58d20da155b90980f27425a99cff2555345fe Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3018303 Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Commit-Queue: Jamie Madill <jmadill@chromium.org>