flyinghead
Add `USE_HOST_X` options
I don't understand what is the point of these changes: vulkan-headers, xxhash, glm and vulkan-memory_allocator are headers-only libraries. So using the host/OS version will not reduce resource usage, will not decrease the executable size and won't allow for easy security updates. It's only adding complexity to the build process and increasing the likelihood of a build failure. Google-test is only used when building and running tests, and isn't part of the final flycast executable. So again, using the host/OS version won't make it easier to package the app.
TBH, I just poked around and did the ones that were trivial. I’ll do more significant ones soon.
Please limit the changes to what is strictly necessary. The build process is already far too complicated for my taste.