[llvm] [SandboxVec] User-defined pass pipeline (PR #108625)

[via llvm-commits]

vporpo wrote:

> For the following patches please make both bots green.
> "The windows bot failure is not related to this patch," can get you in trouble.

These changes are very localized and I am testing them extensively locally. If there is indeed an issue the post-commit bots will notify me and I will revert the patch.



https://github.com/llvm/llvm-project/pull/108625