- Use explicit options when running gmcole.py from run-gcmole.py
- Use gcmole.py-relative paths to find the default V8 root dir for
  maximum convenience when running locally

Change-Id: Iba0da90b99b0321129f1c4099f437c76dabb1186
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3582386Reviewed-by: Maya Lekova <mslekova@chromium.org>
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Auto-Submit: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/main@{#80058}