Select autosiso vs autoninja in rebuild_baselines.py & benchmark.py

Changes gn_helpers.CreateBuildCommand() to use autoninja when no
deps files are present so that scripts work for clean builds.

Bug: None
Change-Id: I5cb4dbb2c718f129ca3856ab66ec043870407956
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4675666
Commit-Queue: Andrew Grieve <agrieve@chromium.org>
Reviewed-by: Peter Wen <wnwen@chromium.org>
Commit-Queue: Peter Wen <wnwen@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1168903}
NOKEYCHECK=True
GitOrigin-RevId: 7c9bc71c46a003cce491e736c96b0e6475e743ea
1 file changed