Investigate `llvm::sys::getHostCPUName()` and `llvm::sys::getHostCPUFeatures()` to possibly improve code generation

[erick-xanadu]

We currently set these to "generic" and "" respectively. While we have the targetMachine->setOptLevel(llvm::CodeGenOptLevel::None); to avoid large compilation times, I believe that using the host cpu name and host cpu features may provide some performance benefits.