Part of my bigger auto{ninja,siso} refactoring.
R=brucedawson@chromium.org, jwata@google.com, tikuta@chromium.org
Bug: b/293657720
Change-Id: I2a7783b8675ecc7dac16a490a290b2edf4b9d64d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/4924716
Reviewed-by: Joanna Wang <jojwang@chromium.org>
Commit-Queue: Joanna Wang <jojwang@chromium.org>
Auto-Submit: Philipp Wollermann <philwo@chromium.org>