Update on Big Sur Problems

[Joshua Root]

Christopher Jones wrote:
> your basic issue is you are enabling by default the gcc5 variant, i.e. you get
> 
> pmm:~ pet$ port variants atlas
> atlas has the variants:
>  gcc49: build using macports-gcc-4.9
>    * conflicts with gcc5 mpclang37 perf
> [+]gcc5: build using macports-gcc-5
>    * conflicts with gcc49 mpclang37 perf
>  mpclang37: use mp-clang-3.7 and gfortran
>    * conflicts with gcc49 gcc5 perf
>  nofortran: Forgo use of fortran compiler
>  universal: Build for multiple architectures
> 
> see the [+] against it above….
> 
> This is not normal, i.e. I get
> 
> Oberon ~/Projects/MacPorts/ports > port variants atlas
> atlas has the variants:
>    gcc49: build using macports-gcc-4.9
>      * conflicts with gcc5 mpclang37 perf
>    gcc5: build using macports-gcc-5
>      * conflicts with gcc49 mpclang37 perf
>    mpclang37: use mp-clang-3.7 and gfortran
>      * conflicts with gcc49 gcc5 perf
>    nofortran: Forgo use of fortran compiler
> 
> 
> Something specific in *your* setup is causing this, and you need to figure out what it is and remove it.

AFAICT, this would happen for all users on arm64. 
<https://github.com/macports/macports-ports/blob/master/math/atlas/Portfile#L154-L159>

Be aware however that last I saw, the atlas maintainer didn't think 
there had been any recent upstream development of this software, and the 
auto-tuning that is the main point of atlas didn't work on any recent 
macOS versions. I don't know if it's even possible to build atlas on 
arm64, but if it's possible, it's probably not worth it.

If it doesn't work, it should set supported_archs and/or known_fail 
appropriately, of course.

- Josh