[lldb] Fix one leak in reproducer

Use a variable of static storage duration to reference an intentionally
leaked variable. A static data area is in the GC-set of various leak
checkers.

This fixes 3 `check-lldb-shell` tests in a `-DLLVM_USE_SANITIZER={Leaks,Address}` build,
e.g. `test/Shell/Reproducer/TestHomeDir.test`

Differential Revision: https://reviews.llvm.org/D100806