Also rolls glslang.

https://chromium.googlesource.com/external/github.com/KhronosGroup/glslang.git/+log/257e9a3f1927..f5ed7a69d5d6

2020-07-03 marcin.slusarz Add --quiet option.
2020-07-05 ShabbyX gn: Fix dawn tests in Chromium
2020-07-05 ShabbyX gn: Fix `gn gen --check` by adding missing dependency
2020-07-03 ShabbyX gn: Optionally disable optimizations and HLSL

Bug: angleproject:4814
Change-Id: Ifcffe72445a315798bf7414b236869055cef5bf0
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2282947
Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>