[llvm-branch-commits] [CI] Run All Tests When Changing third-party (PR #150251)

[Aiden Grossman via llvm-branch-commits]

https://github.com/boomanaiden154 created https://github.com/llvm/llvm-project/pull/150251

This patch ensures that we run all the tests when someone touches
third-party. Some of the projects (like SipHash and Benchmark) do not
get used by every project and we could get away with testing less.
However, it takes quite a bit of effort to tease out what actually does
depend on which library, it is liable to becoming out of date, and it
adds complexity. Just testing all the projects is simple. Given the
commit frequency to third-party is pretty low (a couple commits per
month), we should have no capacity problems here.

Fixes #149154