* I don't like the fact that it doesn't "just work" but this is mostly
limited by design decisions on the side of the vulkan loader.
* There is no good way with the loader to say 'please also include this
layer in the enumerated lists'. There is an all-or-nothing override of
layer searching, but that would break any layers the application might
actually rely on.
* On balance I've decided to go with this method, as it's a one-off
interruption for the user (unless someone is constantly switching
between installs).
baldurk
258e08f740