[lldb] Only use PyConfig when LLDB_EMBED_PYTHON_HOME is enabled (#152588)
PyConfig and friends are not part of the stable API. We could switch
back to Py_SetPythonHome, which has been deprecated, but still part of
the stable API. For now, limit the use of PyConfig to when
LLDB_EMBED_PYTHON_HOME is enabled, which essentially means Windows.
Changing the order doesn't seem to matter.