[scudo] Add a fast get time version.

On Android, the _COARSE version of clock_gettime is about twice as fast.
Therefore, add a getMonotonicTimeFast function that is used in the
releaseToOSMaybe functions.

Reviewed By: Chia-hungDuan

Differential Revision: https://reviews.llvm.org/D145636

GitOrigin-RevId: 32be3405f57f1e4d0ec0da943434113450583e89
Change-Id: I6c66658590851945d2643672f19b4910ca8a8fe6
6 files changed