Currently when the XRay runtime is linked into a binary that doesn't
have the instrumentation map, we print a warning unconditionally. This
change attempts to make this behaviour more quiet by tying it to the
Verbosity setting.
We only print the error when Verbosity is set to anything other than 0.
The Verbosity setting is parsed by the sanitizer_common library, which defines
a common set of flags for the sanitizers. The default verbosity set by
sanitizer_common is 0. XRay already depends on this library and the flags
defined there.