add msys2 CI

[Totto16]

This adds a Msys2 CI.

I tested it in Msys2 Clang64 locally and fixed #365 too.
For that I also had to change some code, so that Msys2 uses windows wide string functions to open a file, otherwise it wouldn't work.

[Totto16]

CI failures are unrelated to this PR, macos-11 isn't available anymore as github runner, and the clang versions that fail are also not available anymore in the ubuntu runners 😓

[uilianries]

I'll send a new PR fixing the CI by today later.

[ColinH]

@uilianries Any update?

[uilianries]

@ColinH Sorry, totally missed it. I'm going to check it now.

[uilianries]

@ColinH Sorry the confusion, the PR #367 is the fix that I mentioned before. Just need a review to be merged.

[ColinH]

Is #367 the only PR that we need to merge now? In other words, did you incorporate the MSYS2 fixes into #367?

[uilianries]

LGTM. The CMake for this build will use Ninja by default.

Android build failed due a checksum mismatch, nothing related to this PR. Still, I would not block it due that failure.

[uilianries]

Is #367 the only PR that we need to merge now? In other words, did you incorporate the MSYS2 fixes into #367?

Yes, I rebased those changes via the commit 8171fc4

[Totto16]

Thank you @uilianries for your work ❤️

[Totto16]

@ColinH would it be possible to have new release, since now mysys2 is fully supported and works again?

[ColinH]

The main branch already has some changes towards a PEGTL 4.0 which I'm otherwise working towards on the work branch; the 4.0 with MSYS2 support will be released when it's ready.