Vulkan: Fix 32-bit Clang build.
Vulkan: Fix 32-bit Clang build.

We were getting a warning:

stdcall calling convention ignored on variadic function

BUG=None

Change-Id: I9165b285dfaf6bc238f946fda2d733292789390d
Reviewed-on: https://chromium-review.googlesource.com/468373
Reviewed-by: Geoff Lang <b6fc25fe0362055230985c05cbfa8adb741ccc0f@chromium.org>

MSOpenTech/angle,ppy/angle,ecoal95/angle,ppy/angle,ecoal95/angle,ppy/angle,ppy/angle,ecoal95/angle,MSOpenTech/angle,ecoal95/angle,MSOpenTech/angle,ecoal95/angle,MSOpenTech/angle