[llvm-branch-commits] [TSan] Make Test work with Internal Shell (PR #165147)

[Aiden Grossman via llvm-branch-commits]

https://github.com/boomanaiden154 created https://github.com/llvm/llvm-project/pull/165147

This test was using subshells to setup LD_LIBRARY_PATH properly. Use a
python script and readfile substitutions to preserve the same behavior.