RFR (S): 8211175: Remove temporary clock initialization duplication

[Robbin Ehn]

Thanks, looks good.

/Robbin

On 10/2/18 8:08 AM, David Holmes wrote:
> webrev: http://cr.openjdk.java.net/~dholmes/8211175/webrev/
> bug: https://bugs.openjdk.java.net/browse/JDK-8211175
> 
> This cleans up some code duplication between os::Linux and os::Posix. os::Posix 
> now exports the necessary clock functions so the Linux code can use those.
> 
> Also cleaned up the clock_getres syscall as that is already provided via the 
> direct clock_getres (no need for a syscall).
> 
> Finally, as code in os::Linux already assumed clock_gettime etc was always 
> available at build-time (and run-time for that matter) this is now explicitly 
> checked via:
> 
> + #ifndef SUPPORTS_CLOCK_MONOTONIC
> + #error "Build platform doesn't support clock_gettime and related functionality"
> + #endif
> 
> Testing: tiers 1-3 (mach5)
> 
> Thanks,
> David