Add guards for 64 bit types on 32bit systems Bug: angleproject:6785 Change-Id: Iff043a22d398f5a7a1a46ae3cc4d2de5a6e3797e Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3331639 Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Kenneth Russell <kbr@chromium.org> Commit-Queue: Gregg Tavares <gman@chromium.org>