Merge pull request #212016 from wegank/opa-platforms

opa: restrict platforms

pkgs/development/compilers/opa/default.nix

···
     homepage = "http://opalang.org/";
     license = lib.licenses.gpl3;
     maintainers = [ ];
-    platforms = with lib.platforms; unix;
+    platforms = [ "x86_64-linux" "x86_64-darwin" ];
   };
 }