tools: explicit path for V8 test tap output

Currently we do not specific an absolute path for the tap output of the
V8 test suite. This is proving to be unreliable across release lines.

By prepending `$(PWD)` to each path we can guarantee it will always be
in the root folder.

PR-URL: https://github.com/nodejs/node/pull/7460


Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com>