[test-suite] Add C-SKY Support in benchmark 1.3.0

[zixuan-wu]

Summary

Use gettimeofday to get the number of cycles since power-on in CSKY backend.

[lebedev.ri]

Please can you submit this upstream first?

[zixuan-wu]

The same work has been upstreamed at https://github.com/google/benchmark/pull/1400.
And how is this patch going? we need pull latest code to upgrade benchmark or still commit this in llvm-test-suite?
@mtrofin

[mtrofin]

In D100926#3533685, @zixuan-wu wrote:

The same work has been upstreamed at https://github.com/google/benchmark/pull/1400.
And how is this patch going? we need pull latest code to upgrade benchmark or still commit this in llvm-test-suite?
@mtrofin

It'd be best to pull from upstream, but if that is too big of a change, fine to patch here.

[zixuan-wu]

In D100926#3534376, @mtrofin wrote:

In D100926#3533685, @zixuan-wu wrote:

The same work has been upstreamed at https://github.com/google/benchmark/pull/1400.
And how is this patch going? we need pull latest code to upgrade benchmark or still commit this in llvm-test-suite?
@mtrofin

It'd be best to pull from upstream, but if that is too big of a change, fine to patch here.

I think this change is nit, if pull from upstream, the change is big and may cause regression.
Since you processed the last pull merge, could you please process this again, or we just continue to do this patch? I am OK with both solutions.

MicroBenchmarks/libs/benchmark-1.3.0/src/cycleclock.h

if (pmcntenset & 0x80000000ul) {  // Is it counting?
       // The counter is set up to count every 64th cycle
       return static_cast<int64_t>(pmccntr) * 64;  // Should optimize to << 6
     }
   }
 #endif
   struct timeval tv;
   gettimeofday(&tv, nullptr);
   return static_cast<int64_t>(tv.tv_sec) * 1000000 + tv.tv_usec;
-#elif defined(__mips__) || defined(__m68k__) || defined(__csky__)
+#elif defined(__mips__) || defined(__m68k__)
   // mips apparently only allows rdtsc for superusers, so we fall
   // back to gettimeofday.  It's possible clock_gettime would be better.
   struct timeval tv;
   gettimeofday(&tv, nullptr);
   return static_cast<int64_t>(tv.tv_sec) * 1000000 + tv.tv_usec;
 #elif defined(__s390__) // Covers both s390 and s390x.
   // Return the CPU clock.
   uint64_t tsc;