[llvm] [GitHub] Set top level token permission (PR #87326)

[Marius Brehler via llvm-commits]

marbre wrote:

> This seems reasonable of course, but as always with these kinds of changes - It's really hard to test ahead of time to make sure it doesn't break anything. Have you tested this in your fork?

So far I've checked what actions are used within the workflow, but this cannot be considered at testing ahead. I had in mind that this workflow isn't that critical and that it is partly ignored (if I remember one of the pre-merge check discussions correctly). However, I converted this PR to a draft PR and will take a closer look and test within my fork.

https://github.com/llvm/llvm-project/pull/87326