Hardware::CPU: more arm fixes (#351)
Hardware::CPU: more arm fixes (#351)

* Better CPU bits detection using `getconf LONG_BIT` instead of
  `/proc/cpuinfo`. The latter one may return CPU info for host
  computer when running brew inside VM.
* Fix arch_32_bit/arch_64_bit to return correct arch for arm.
Linuxbrew/brew,rwhogg/brew,Linuxbrew/brew,rwhogg/brew,hanxue/linuxbrew,maxim-belkin/brew,hanxue/linuxbrew,hanxue/linuxbrew,rwhogg/brew,maxim-belkin/brew,maxim-belkin/brew,Linuxbrew/brew,Linuxbrew/brew