Now it's even simpler, and it now generates multiple
shader languages at once! The copying mechanism is now
much simpler on non-mac platforms as well. HLSL is also now a supported shader target language.
This is laying some groundwork for a much better way
of determining the best GFX api to use at runtime, and
making it easier to support more GFX backends in the future.
This is shipped by SDL2 itself, so it should be the preferred way
of finding it. Since SDL2 does not ship it in their Windows
development libraries, we still need to use the regular Find module.
