Do not restrict "weak authority" option to Android

libusb_wrap_sys_device() is an often needed feature on Android, but can
also be very convenient on other Linux platforms.

In many cases the initial device scanning is not needed and
LIBUSB_OPTION_WEAK_AUTHORITY thus provides a performance enhancement.

Closes #925

Signed-off-by: Tormod Volden <debian.tormod@gmail.com>
Signed-off-by: Nathan Hjelm <hjelmn@google.com>