Nuke support for running MSan without a simulator.

We've abandoned that approach. The ARM64 simulator is the only supported way of
running V8 under MSan.

R=jkummerow@chromium.org

Review URL: https://codereview.chromium.org/493923003

Patch from Sergey Matveev <earthdok@chromium.org>.

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@23882 ce2b1a6d-e550-0410-aec6-3dcde31c8c00