It was only being used for fs::remove() (added in #3463), which is easily
replaced by std::remove().
The code change does not affect the WPILib tools, as this code is not used when JSON save files are used.
The CMake enable/disable flags as currently structured are a confusing mix of
WITH, WITHOUT, and USE with odd defaults. This changes the flags to consistently
use WITH and default the build options to everything enabled.
These hide the platform specifics behind a common C++ API. Platforms:
- Windows: DirectX 11 (with 10 backwards compatibility)
- Linux: OpenGL 3
- Mac: Metal
