Disable detection of bugs on global variables.

This is a temporary change pending code cleanup.

We are already disabling detection of ODR violations. As it turns out,
an ODR between an ASan-instrumented library and a non-instrumented library
may actually crash ASan, and there is no obvious way out, and one of those
prevents us from booting a SANITIZE_TARGET image right now.

Bug: 21951850
Change-Id: I49508242ec96089a3d4d8b7e45f36323d62f2be9