[llvm] r209420 - Extend sys::getHostCPUFeatures to work on AArch64 platforms

[Tim Northover]

Hi Bradley,

> +  enum {
> +    HWCAP_AES   = 0x1,
> +    HWCAP_PMULL = 0x2,
> +    HWCAP_SHA1  = 0x4,
> +    HWCAP_SHA2  = 0x8
> +  };

I happened to try building LLVM on AArch64 this evening; it seems
asm/hwcap.h gets included via some route and #defines these
enumerators, so the build fails. With luck, the bot will pick it up
soon too, but just in case...

Cheers.

Tim.