[llvm] [llvm][lit] fix writing results to file (PR #130845)

[James Henderson via llvm-commits]

https://github.com/jh7370 approved this pull request.

Just to clarify: is lit unconditionally failing with a python error here, because `time_trace_file` is an unknown identifier?

If so, LGTM, assuming that `self.output_file` is a file path and not a file object... (I haven't dug into all the code).

https://github.com/llvm/llvm-project/pull/130845