I was having trouble building the library in totality due to some errors in the projectm-test-ui project. I was able to trace the errors to the includes in the file pmSDL.hpp. By tweaking the order to go in the order at which matches the call stack (this is I think the source of the issue. D needs C needs B needs A, so I set it to A, B, C, D, if that makes sense)
I also used vcpkg to install dependencies, so I added the ./vcpkg-install directory to .gitignore so that people who also use vcpkg don't accidentally push their dependencies to their own or the main repo.
Fixed-up branch for PR #650 per @serjykalstryke.