llvm dev - Dec 2018 - error: instruction requires: AVX-512 ISA

Hi Everyone,

We caught a bug report at
https://github.com/weidai11/cryptopp/issues/753 . It looks like an
issue that is local to Xcode and OS X Mojave. I don't have a new
MacBook so I can't test things and gain an understanding of what is
happening.

The command line is "CXX=g++ make ...", so OP is using a modern GCC
compiler and Clang toolchain. The makefile adds `-Wa,-q` for the ports
compiler so the Clang Integrated Assembler is being used to assemble
the code.

Based on the bug report, does anyone have an idea of what is happening
and how to fix it?

I don't like the proposed solution of adding -march=native. It breaks
other use cases, like folks who distribute their software.

(I know this is pretty shitty report. It is all I have at the moment.
Sorry about that).

Jeff