CICD won't build macOS due to SDK download no longer being available

[Raelr]

Currently, the entire project depends on the Vulkan SDK to be available to build. This creates a dependency that can't easily be replicated in a CICD environment.

At the moment, the CICD system will manually download the SDK to the VM and run the tests from there. This works for Windows and Linux, however MacOS breaks due to a change in the format the SDK is provided in. As such, a new solutions needs to be found to make this work correctly.

This issue is for changing the build system to pull in the Vulkan dependencies and manually build them. This has the following advantages:
a) Allows the renderer to be build and tested in CICD.
b) Allows Vulkan to be shipped without the end user requiring the Vulkan SDK.

[Raelr]

Note: looks like manually building the SDK will require either the VK_LAYER_PATH and VK_ICD_FILENAMES variables to be set. This can be circumnavigated by installing the validation layers to the user's usr/local/share folder.