Update build.rs to handle CMake build system

[talklittle]

Upstream libui has changed to a CMake build system.

ui-sys/build.rs should be updated to handle it.

[talklittle]

It looks like @Machtan already has a working build.rs that handles CMake!

https://github.com/Machtan/libui-rs/blob/3f5f79dce7701b38783763da14f97f14f2b140c0/ui-sys/build.rs

@Machtan, would you be willing to submit a PR for that?

Sure. The version of the libui submodule referenced might have to be changed, though. At least I get a crash on the controlgallery example and weird artifacts on the rust logo one.

The pull request is made. (I got it to use alpha3 too, but the examples are still unusable on Mac)

[talklittle]

Cool thanks! Actually I believe alpha3 is just before the CMake changes upstream. I guess your build.rs is robust enough to handle both old and new build systems.

Anyway, I made pull request #3 to fix the controlgallery.rs example, tested on Mac, but haven't attempted to fix the Rust logo artifacts.

I just realized the thing about alpha3, so now it's gone again. Should I update to include the ~10 CMake related commits made since yesterday?

[talklittle]

Sure, I think that would be really cool. It's all up to you though. I'm not a maintainer of this library, so my suggestions don't necessarily matter much. :)

[zentner-kyle]

I have a pull request up now which I think solves this issue. #14