[llvm] [Support] Assert that DomTree nodes share parent (PR #101198)

[via llvm-commits]

dyung wrote:

I don't think this is strictly related to ccache. We are seeing many internal tests fail with the exact same assertion failure message that I am now trying to bisect and highly suspect this change as it is the only one in the range that seems likely to have caused the issue.

https://github.com/llvm/llvm-project/pull/101198