This allows measuring the delay between events more accurately if a
device is often suspended.
While CLOCK_BOOTTIME would be preferable, Android's bionic C library
does not support it for condvars.
While building against this level in general would break our app on
older systems, the NDK will automatically use this level for 64-bit
ABI builds (which are not supported in older levels). So to build
against 64-bit ABIs we have to support this API level.