Make run.py re-exec itself.
Make run.py re-exec itself.

Turns out I'm wrong and the shebang is relative to cwd, not to the script.
Useless.

R=agable@chromium.org, vadimsh@chromium.org
BUG=

Review URL: https://codereview.chromium.org/418483005

nicko96/Chrome-Infra,nicko96/Chrome-Infra,nicko96/Chrome-Infra,nicko96/Chrome-Infra,nicko96/Chrome-Infra