With --debug-code specified, 8 KB is not sufficient to contain
some of the builtins on PPC64.

This path is relevant only when snapshots are off.

R=rmcilroy@chromium.org, ulan@chromium.org, michael_dawson@ca.ibm.com
BUG=

Review URL: https://codereview.chromium.org/1415463002

Cr-Commit-Position: refs/heads/master@{#31449}