atlas: build on Linux only

Fixes #10808.

pkgs/development/libraries/science/math/atlas/default.nix

···
     homepage = "http://math-atlas.sourceforge.net/";
     description = "Automatically Tuned Linear Algebra Software (ATLAS)";
     license = stdenv.lib.licenses.bsd3;
+    platforms = stdenv.lib.platforms.linux;
 
     longDescription = ''
       The ATLAS (Automatically Tuned Linear Algebra Software) project is an