CI: use MSYS2 cargo package for example project

[mgeier]

I recently found out that there is a Rust package for MSYS2 (https://packages.msys2.org/base/mingw-w64-rust), and there is even a package for cargo-c (https://packages.msys2.org/base/mingw-w64-cargo-c)!

I tried to use the Rust package on CI, but still compile the latest version of cargo-c on the fly.

Sadly, there are a few problems ...

Currently, there is a build error during cargo cinstall, any ideas how to fix this?

After that, there might still be a problem with the library not being installed into the default location normally used for MSYS2, but for now that's blocked by the compilation error.

There seems to be another error in the Windows build (the one without MSYS2), which should also be solved, but it isn't really related to this PR.

[codecov-commenter]

Codecov Report

Merging #194 (749ac88) into master (b84d67a) will not change coverage.
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  Misses        277      277           

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[mgeier]

I've just re-based this PR and the error still occurs:

     Running `rustc --crate-name libc 'C:\Users\runneradmin\.cargo\registry\src\github.yoyoweb123.workers.dev-1ecc6299db9ec823\libc-0.2.98\src\lib.rs' --error-format=json --json=diagnostic-rendered-ansi --crate-type lib --emit=dep-info,metadata,link -C opt-level=3 -C embed-bitcode=no -Cpanic=abort --cfg 'feature="default"' --cfg 'feature="std"' -C metadata=484b93cfa35492db -C extra-filename=-484b93cfa35492db --out-dir 'D:\a\cargo-c\cargo-c\example-project\target\x86_64-pc-windows-msvc\release\deps' --target x86_64-pc-windows-msvc -L 'dependency=D:\a\cargo-c\cargo-c\example-project\target\x86_64-pc-windows-msvc\release\deps' -L 'dependency=D:\a\cargo-c\cargo-c\example-project\target\release\deps' --cap-lints allow --cfg freebsd11 --cfg libc_priv_mod_use --cfg libc_union --cfg libc_const_size_of --cfg libc_align --cfg libc_core_cvoid --cfg libc_packedN --cfg libc_cfg_target_vendor`
error[E0463]: can't find crate for `core`
  |
  = note: the `x86_64-pc-windows-msvc` target may not be installed

error: aborting due to previous error

For more information about this error, try `rustc --explain E0463`.
error: could not compile `libc`

[mgeier]

I finally managed to make this work!

I had to manually specify --target and --prefix, which isn't very nice IMHO.
This shouldn't be a blocker for merging this PR, but in the future it would be nice if we could avoid those.

[lu-zero]

I guess cargo has the msvc toolchain as default.

[mgeier]

Yeah, looks like it.

I was hoping to get the right target automatically, since I'm using cargo from MSYS2, which should know that it uses the GNU toolchain.

Strangely, when I'm using the MSYS2 package for cargo-c (instead of compiling it on-the-fly), the --target flag is not necessary (see https://github.com/mgeier/cargo-c/runs/4754623622)!

So why does the MSYS2 package of cargo-c do the right thing?

But, as I said, I don't think this should be a blocker for now, we can try to figure this out later.

[mgeier]

I've created a separate issue as a reminder: #244.

[mgeier]

For completeness, I've also created one about the --prefix: #245

[lu-zero]

Thank you!