Add support for UWP targets
Hi,
This pull request aims at adding support for UWP (Universal Windows Apps) platform.
A few notes:
- This requires a very recent mingw-w64 version (containing this commit and the previous related ones: e8c433c871 (diff-eefdfbfe9cec5f4ebab88c9a64d423a9))
- This was tested using LLVM/clang rather than gcc, and so far it assumes that LLVM/clang will be the native compiler. This is mostly due to the fact that the support for exceptions/stack unwinding for UWP got much more attention in libunwind
- The "uwp" part of the target needs support for it in the `cc-rs` & `backtrace-rs` crates. I'll create the MR there right after I submit this one and will link everything together, but I'm not sure what's the correct way of dealing with external dependencies in the context of rust
- Enabling import libraries and copying them across stages requires a change in cargo, for which I'll open a MR right after I submit this one as well
- The i686 stack unwinding is unsupported for now, because LLVM assumes SjLj, while rust seems to assume SEH will be used. I'm unsure how to fix this
Also, this is my first encounter with rust, so please bear with my code, it might not feel so idiomatic or even correct :)
I'm pretty sure there's a way of doing things in a cleaner way when it comes to win/c.rs, maybe having a UWP & desktop specific modules, and import those conditionally? It doesn't feel right to sprinkle `#[cfg(...)]` all over the place
Off course, I'll gladly update anything you see fit (to the extent of my abilities/knowledge :) )!
Thanks,
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