Better cross compilation support

[messense]

Originally I want to use autotools-rs, but it doesn't support Rust 1.36.0.

This enables building with cargo-zigbuild:

cargo zigbuild --target x86_64-unknown-linux-gnu

[yorickpeterse]

Windows GNU builds are failing with the following error:

  = note: D:\a\libffi-rs\libffi-rs\target\debug\build\libffi-sys-5c1d0e050ef2f003\out\libffi-root\lib\libffi.a(closures.o): In function `internal_malloc_stats':
          D:\a\libffi-rs\libffi-rs\target\debug\build\libffi-sys-5c1d0e050ef2f003\out\libffi-build\x86_64-pc-windows-gnu/../src/dlmalloc.c:2951: undefined reference to `__imp___acrt_iob_func'
          D:\a\libffi-rs\libffi-rs\target\debug\build\libffi-sys-5c1d0e050ef2f003\out\libffi-build\x86_64-pc-windows-gnu/../src/dlmalloc.c:2952: undefined reference to `__imp___acrt_iob_func'
          D:\a\libffi-rs\libffi-rs\target\debug\build\libffi-sys-5c1d0e050ef2f003\out\libffi-build\x86_64-pc-windows-gnu/../src/dlmalloc.c:2953: undefined reference to `__imp___acrt_iob_func'

I'm guessing some compile options may be missing?

[messense]

x86_64-pc-windows-gnu test only fails on Rust 1.36.0, kinda odd, I'm not sure why.

Here is a related stackoverflow post: https://stackoverflow.com/questions/62804616/cross-compiling-from-linux-windows-stdio-has-undefined-references-to-imp-a

[yorickpeterse]

@messense Past builds/PRs worked just fine though, so this is the result of something that the cc crate is doing. Since Rust 1.36 is ancient at this point I'm fine with bumping the minimum version (e.g. to 1.48 as Debian stable seems to still be using that), but not if newer versions of Rust are also failing. Could you check to see how newer versions are doing? Thanks!

[messense]

Test passed on Rust 1.48.0.

https://github.com/messense/libffi-rs/runs/5441820451?check_suite_focus=true

[messense]

rust-lang/rust#67429 might be related, it was released in Rust 1.43.0.

[yorickpeterse]

@messense Thanks! This has been released in libffi-sys 2.0 and libffi-rs 3.0 🎉