clang build fix march=native is unsupported

[devnexen]

No description provided.

[Screwtapello]

Which versions of clang do not support -march=native?

$ clang --version
Debian clang version 11.0.1-2
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/bin
$ clang -march=native -o werder werder.c
$ ls -l werder
-rwxr-xr-x 1 st st 16864 Mar 20 22:40 werder

[devnexen]

clang/xcode specifically (Mac M1)

[jchv]

In general, clang does support this flag, on x86 machines, so it is not a good idea to not set it whenever clang is being used. Detecting that we’re on a setup that doesn’t support -march will require some better detection. For now my workaround for the problem is to just pass local=false to make when building on M1.

[Screwtapello]

After some scrounging around, I found an article discussing tuning flags across ARM and x86. Apparently -march, -mcpu and -mtune mean different things, and x86's -march is roughly equivalent to ARM's -mcpu, it doesn't have anything to do with macOS, and it's not even specific to Clang/LLVM (although GCC is friendlier to x86 compiler flags).

[devnexen]

seems to work on Mac M1.

[Screwtapello]

Thank you for looking into this! I've made an expanded version of this change in #167, preserving you as the patch author. If you could look over that change and confirm I haven't missed anything, I'll land it.

[devnexen]

All good

[Screwtapello]

I've merged #167, so higan should build cleanly on M1 Macs by default now. Again, thank you for your help!