sandbox: Add Arm64 support for seccomp-BPF

Adds support for Arm64 to 'sandbox/'. This can be used
by future CLs to provide Arm64 policy for Chrome.

BUG=355125
TEST=sandbox_linux_unittests

Review URL: https://codereview.chromium.org/487143003

Cr-Commit-Position: refs/heads/master@{#291631}
15 files changed