Replace platforms.linux with platforms.darwin for expressions that compile on darwin too (too restrictive platforms)

pkgs/development/python-modules/pyicu/default.nix

@@ -30,7 +30,7 @@ buildPythonPackage rec {
     homepage = https://pypi.python.org/pypi/PyICU/;
     description = "Python extension wrapping the ICU C++ API";
     license = licenses.mit;
-    platforms = platforms.linux; # Maybe other non-darwin Unix
+    platforms = platforms.unix;
     maintainers = [ maintainers.rycee ];
   };