build: Add more error checking for build environment
build: Add more error checking for build environment

Make sure that a KHRONOS_ACCOUNT_NAME and necessary BIL
files exist before doing any other work. That way user
knows right away if build environment is setup correctly or not.

KhronosGroup/Vulkan-Tools,KhronosGroup/Vulkan-Tools,KhronosGroup/Vulkan-Tools,KhronosGroup/Vulkan-Tools