sandbox: sandbox_linux_unittests enforces TSYNC on ChromeOS

Make Seccomp-bpf tsync support mandatory on ChromeOS now
that all kernels support it.

BUG=
TEST=ChromeOS trybots

Review URL: https://codereview.chromium.org/759343002

Cr-Commit-Position: refs/heads/master@{#306673}
1 file changed