As required by #sec-built-in-function-objects.
They were strict functions before (see
e2f1c269), but that got lost when they
were ported to ASM builtins.
This makes optimized and non-optimized code agree on the same behavior
in regress-105.js.

BUG=v8:105,v8:5778,v8:6325

Review-Url: https://codereview.chromium.org/2848313004
Cr-Commit-Position: refs/heads/master@{#45012}