This commit adds special cases for AccelerationStructureInstanceKHR and
VkAccelerationStructureSRTMotionInstanceNV. These types use bit-packed
fields which are not representable in the current version of the zig
stage 2 compiler. This might change when
https://github.com/ziglang/zig/issues/13009 is resolved.
Fixes#56
Current setup works fine if passed static memory like '&.{ "glslc" }', but produces errors of various types (segmentation faults, access denied, file doesn't exist, etc) if passed a dynamically allocated slice, such as a slice containing the result of a call to `Builder.pathJoin`, a la `b.pathJoin(&.{ b.env_map.get("VULKAN_SDK").?, "bin", "glslc" })`.
