The option lets us use the function in cases where we cannot use the current
version due to restrictions on src and dst. This will be useful for some arm64
builtins when we pad the stack arguments, where we will need to copy the
existing arguments either one slot up or one slot down in memory.

Bug: v8:6644
Change-Id: I75281cdc9fa6812e3b24bf5756057c93305cbb95
Reviewed-on: https://chromium-review.googlesource.com/771711Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Commit-Queue: Georgia Kouveli <georgia.kouveli@arm.com>
Cr-Commit-Position: refs/heads/master@{#49394}