compiling ArcticFox on 10.11 - atomic not found, cxx11

[Ken Cunningham]

$ cat atomic.cxx
#include <atomic>
int main(void) {
return (0);
}

$ clang++-mp-9.0 -stdlib=libstdc++ atomic.cxx
atomic.cxx:1:10: fatal error: 'atomic' file not found
#include <atomic>
    ^~~~~~~~
1 error generated.


$ clang++-mp-9.0 -stdlib=macports-libstdc++ atomic.cxx
<OK>

h$ clang++-mp-9.0 -stdlib=libc++  atomic.cxx
<OK>