Take the build level into account for the version hash

build is the third number of the V8 version, and very likely to change
(in contrast to the patch level which typically is zero on canaries).

BUG=chromium:440984
R=mvstanton@chromium.org,yangguo@chromium.org
LOG=n

Review URL: https://codereview.chromium.org/802363002

Cr-Commit-Position: refs/heads/master@{#25820}