Abort if we fail to run the program to determine V8 version

Change-Id: Ibd9d3c96ec0b67a1bbebbfade3cb7eb9dd74b682
Reviewed-on: http://review.couchbase.org/43842
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Dave Rigby <daver@couchbase.com>