Externals: Update glslang.

This updates glslang to commit 4fc7a33910fb8e40b970d160e1b38ab3f67fe0f3
which is the current version listed in the known_good.json file for the
version 1.2.131.2 of the Vulkan-ValidationLayers repo.

Externals/glslang/SPIRV/bitutils.h

@@ -26,7 +26,7 @@ Dest BitwiseCast(Src source) {
   Dest dest;
   static_assert(sizeof(source) == sizeof(dest),
                 "BitwiseCast: Source and destination must have the same size");
-  std::memcpy(&dest, &source, sizeof(dest));
+  std::memcpy(static_cast<void*>(&dest), &source, sizeof(dest));
   return dest;
 }