benchmark

cycleclock: Use cock_gettime() as fallback for any Linux architecture (#1899)

The Linux kernel provides the clock_gettime() functions since a long
time already, so it's possible to use it as a generic fallback option
for any architecture if no other (better) possibility has been provided
instead.

I noticed the benchmark package failed to build on debian on the SH-4
architecture, so with this change SH-4 is now the first user of this
fallback option.