[llvm] [utils][tests] Adjust timeout-hang.py tolerances (PR #142089)

[David Spickett via llvm-commits]

https://github.com/DavidSpickett commented:

I know the pain of dealing with these, and trying to explain them to folks that sometimes real, actual time is important to computers :)

I had never thought to handle it this way though.

If lit were to hang trying to execute the non-existent program: this all takes 15 seconds, this test fails
If lit immediately returns: it takes significantly less than 15 seconds, this test passes (it will take more or less time depending on when the parent lit process gets cpu time)

https://github.com/llvm/llvm-project/pull/142089