This relaxes the check if the test262 archive should be unpacked or not.
A bug in the swarming isolate processor for windows makes the old check for the data directory pass and not unpack.
With this work-around we actually start running tests on windows.

This also fixes the regexp for exception extraction and handles the windows drive letter.
It also strips whitespace to fix a case where a carriage return was included on windows.

BUG=v8:5872

Change-Id: I363925665b0bad7530a1f93a2ea8f39b056d4174
Reviewed-on: https://chromium-review.googlesource.com/445786
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Reviewed-by: Daniel Ehrenberg <littledan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#43482}