SystemStats wrong under AARCH64 emulation on Linux

In juce_linux_SystemStats.cpp the capabilites of the CPU are determined by reading /proc/cpuinfo. When running under emulation (e.g. via aarch64 docker image on x86_64) Intel features will be set. e.g. hasAVX2 even though we are running on ARM emulation.

I think it might be better to share the Intel x86/x86_64 parts of the CPU info code across Windows/macOS/Linux and base it all on cpuid instructions.