Missing HWCAP definitions for x86_64 #2929
Description
Target Triple: stable-x86_64-unknown-linux-gnu
API: https://github.com/torvalds/linux/blob/master/arch/x86/include/asm/cpufeatures.h
The aarch64 target enjoys HWCAP fields (bitfields in the returned value from getauxval(AT_HWCAP), but these constants are absent in glibc and musl x86_64. Can we add them? These are effectively the X86_FEATURE_* constants