Eliminate boilerplate of having each test manually assign to `mydir` by calling
`compute_mydir` in lldbtest.py.
Differential Revision: https://reviews.llvm.org/D128077
This reverts commit 3bf96b0329be554c67282b0d7d8da6a864b9e38f.
It causes crashes as reported in PR52257 and a few other places. A reproducer is bundled with this commit to verify any fix forward. The original test is left in place, but marked XFAIL as it now produces the wrong result.
Reviewed By: teemperor
Differential Revision: https://reviews.llvm.org/D113449
