`set([primary_solution_path, gclient_root_path, gclient_src_root_path])` doesn't guarantee order.
This is problematic when `SISO_PATH` is used because it doesn't check the presence of `third_party/siso/siso` binary.
This CL changes siso.py to check the presence of `.sisoenv` to detect the correct `base_dir`.
Change-Id: Ieb1acc44269037d43c793eb28cd2f12ad0179b17
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/4625315
Auto-Submit: Junji Watanabe <jwata@google.com>
Commit-Queue: Junji Watanabe <jwata@google.com>
Reviewed-by: Philipp Wollermann <philwo@google.com>
Reviewed-by: Fumitoshi Ukai <ukai@google.com>