These tests assume that it is OK to switch between time implementations,
but the clock_gettime call uses CLOCK_MONOTONIC and the fallback call,
gettimeofday, uses CLOCK_REALTIME. Disabling the clock_gettime call means
that calls to nanotime will start returning very different values.
This breaks the new timer code, which assumes that nanotime will return
a consistently increasing value.
This test is not very useful in any case as it doesn't check the results.
Removing this file also removes BenchmarkTimeNow, which is a duplicate
of BenchmarkNow in the time package.