[#774] implement GetNumCPUs(), GetCPUCyclesPerSecond(), and GetCacheSizes() (#775)
[#774] implement GetNumCPUs(), GetCPUCyclesPerSecond(), and GetCacheSizes() (#775)

- On qnx platform, cpu and cache info is stored in a syspage struct which
  is different from other OS platform.
- The fix has been verified on an aarch64 target running qnx 7.0.
Fixes #774
mockingbirdnest/benchmark,mockingbirdnest/benchmark,mockingbirdnest/benchmark,google/benchmark,google/benchmark,mockingbirdnest/benchmark,google/benchmark