[compiler-rt] [llvm] [compiler-rt][test] Resolved export command failure in test run with lit's internal shell (PR #105961)

[Paul Kirth via llvm-commits]

https://github.com/ilovepi requested changes to this pull request.

I'm fine w/ the code change in TestRunner.py, but 

1) this needs a test in lit's test suite
1) the compiler-rt change should be split out on its own

https://github.com/llvm/llvm-project/pull/105961