Vulkan Loader and Validation Layers on Fuchsia

• The BUILD.gn files are for building as a part of Fuchsia using GN.
• The build-fuchsia directory contains customized scripts to generate some of the necessary header files. They are used in the root BUILD.gn file.
• The header files vulkan.h and vulkan.hpp are generated from vk.xml. If vk.xml changes, regenerate the files with the following steps:

# Before you start, $FUCHSIA_ROOT must point to the root of your
# Fuchsia checkout. Then use that to set $VULKAN_LOADER_SOURCE:
export VULKAN_LOADER_SOURCE=$FUCHSIA_ROOT/third_party/vulkan_loader_and_validation_layers

# Check out Vulkan-Hpp repository
git clone --recursive https://github.com/KhronosGroup/Vulkan-Hpp.git
cd Vulkan-Hpp

# Copy over our version of vk.xml
cp $VULKAN_LOADER_SOURCE/scripts/vk.xml Vulkan-Docs/src/spec/vk.xml

# Generate header files from vk.xml
cmake . && make && ./VulkanHppGenerator
(cd Vulkan-Docs/src/spec && make clobber install)

# Copy the header files back to our repo
cp vulkan/vulkan.hpp $VULKAN_LOADER_SOURCE/include/vulkan/vulkan.hpp
cp Vulkan-Docs/src/vulkan/vulkan.h $VULKAN_LOADER_SOURCE/include/vulkan/vulkan.h