[llvm] [lit] Ignore src permissions when copying lit_test_times (PR #121377)

[Thomas Preud'homme via llvm-commits]

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

I had no idea cp tried to keep the same permission. Since this is a workaround I'll give some time for people to reply if they have a better (portable) idea.

https://github.com/llvm/llvm-project/pull/121377