disable rtti by default even for non-bionic builds

With this change, we'll use same the logic to determine whether to
disable RTTI for all targets. Previously, there was no way to disable
RTTI for glibc or musl host builds.

Bug: 341341056
Test: m
Change-Id: I096ddf54314c7692d4a82f549e2071471a6c72f3