On some architectures the InvokeBuiltin sequence does not go through
InvokeFunctionCode, which initializes the new.target register. This
initializes the register explicitly on these architectures for now.

R=ishell@chromium.org
BUG=chromium:565046
LOG=n

Review URL: https://codereview.chromium.org/1499953002

Cr-Commit-Position: refs/heads/master@{#32622}