stack.py: Don't assume --chrome-symbols-dir values are relative to DIR_SORUCE_ROOT

This tripped me up. It's much less surprising to interpret relative
paths as being relative to CWD.

I could find no checked-in usages of this flag, so hopefully does not
break anything.

Change-Id: I6b6db76f2583027e5bc3eba15f49dd32b1b37bf3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3370067
Auto-Submit: Andrew Grieve <agrieve@chromium.org>
Reviewed-by: Siddhartha S <ssid@chromium.org>
Commit-Queue: Siddhartha S <ssid@chromium.org>
Cr-Commit-Position: refs/heads/main@{#956653}
NOKEYCHECK=True
GitOrigin-RevId: c7ff2988bf93f1ec508ec103d2d53a96e194ef34
1 file changed
tree: d65df3082c24a76b3e0829c37959b5f352f6135e
  1. development/
  2. DIR_METADATA
  3. LICENSE
  4. OWNERS
  5. README.chromium