Add formatting check to CI pipeline

[Vexu]

Reopening of #8219 now that the parsing issue has been fixed. I also added a check-ast on the self hosted compiler main.zig since that should also test the standard library.

[g-w1]

Ast-check does not follow imports, so you should do find .. -name "*.zig" | xargs ./zig ast-check or something similar.
Also, ./zig fmt --check .. should work and it is more simple.

[andrewrk]

I suggest we only do the zig fmt check for now, for a few reasons:

• This doesn't actually check any files other than src/main.zig
• std lib AST checking is already happening with every stage2 test
• It's an unrelated change to adding zig fmt checking
• we may want to consider taking advantage of the thread pool and cache, which is already happening with std lib AST checking

[Vexu]

* This doesn't actually check any files other than src/main.zig

Solved with find . -name "*.zig" ! -path "*/zig-cache/*" ! -path "*/zig-out/*" | xargs -n1 release/bin/zig ast-check.

* std lib AST checking is already happening with every stage2 test

Std files can be easily excluded in the command.

* It's an unrelated change to adding zig fmt checking

Sure, it did find a some bugs in stage2 and a lot of nonconforming code everywhere else so it might be better to do separately.

* we may want to consider taking advantage of the thread pool and cache, which is already happening with std lib AST checking

It takes less than 15 seconds to check all ~900 files on my laptop on a debug build, I don't think performance is going to be that big of an issue.

[g-w1]

Why was this changed? I think ../std.zig is more correct.

[Vexu]

There is a pretty much even divide between @import("std.zig") and @import("std"), I changed this because I wanted to test this file specifically.

[andrewrk]

Generally, std lib should import std.zig by file path, setting an example for other packages. For zig test you can use --main-pkg-path to test files that import with "..".

[Vexu]

$ hyperfine "zig-out/bin/zig fmt . --ast-check --check" --warmup 1
Benchmark #1: zig-out/bin/zig fmt . --ast-check --check
  Time (mean ± σ):      6.056 s ±  0.022 s    [User: 2.499 s, System: 3.552 s]
  Range (min … max):    6.022 s …  6.094 s    10 runs

Not too bad for ~860 files.