Add a note on why ANGLE is pinned to C++17 vulkan_memory_allocator uses std::popcount conditionally on C++20, and it's currently missing from external/libcxx as it wasn't updated yet Bug: b/311052584 Bug: b/175635923 Change-Id: I51728cfa13ccb5c24eab13baabb8c08b275e258f Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/5238766 Commit-Queue: Roman Lavrov <romanl@google.com> Auto-Submit: Roman Lavrov <romanl@google.com> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>