Update LLVM to 13.0.1

[chalcolith]

This change updates our LLVM submodule to llvmorg-13.0.1

[ponylang-main]

Hi @kulibali,

The changelog - changed label was added to this pull request; all PRs with a changelog label need to have release notes included as part of the PR. If you haven't added release notes already, please do.

Release notes are added by creating a uniquely named file in the .release-notes directory. We suggest you call the file 3994.md to match the number of this pull request.

The basic format of the release notes (using markdown) should be:

## Title

End user description of changes, why it's important,
problems it solves etc.

If a breaking change, make sure to include 1 or more
examples what code would look like prior to this change
and how to update it to work after this change.

Thanks.

[SeanTAllen]

Interesting: the identity_nested_tuple test failed on Windows.

[SeanTAllen]

@kulibali did you rerun the failed Windows run?

[chalcolith]

Yes.

[SeanTAllen]

@kulibali it seems very odd to have that test be fail then not fail. Do you think it was a runner bug?

[chalcolith]

It might have timed out for some reason.

[SeanTAllen]

I don't see how. It's a very simple test in the middle of the runner suite.

[chalcolith]

I observed during development that sometimes processes took a while to start on Windows, so my suspicion is that the compile and run steps might be taking too long for some Windows reason.

[SeanTAllen]

Hmmm I've never seen before, so probably rare. Any thoughts on anything we could do to address?