sift: fix hydra build fail (#16820)

For some reason I haven't been able to figure out, sift does not build on OSX.
I think it is because sift uses cgo for some of its functionality which you can
see here:
https://github.com/svent/sift/blob/master/matching_cgo.go#L23

The error which hydra found (and is reproducible on OSX) can be seen here:
https://hydra.nixos.org/build/37169149

Ideally I would like to get sift building on OSX, however my nix-fu is weak.
Any suggestions are welcome. In the meantime I would like to get sift into one
of the release channels for Linux where it works fine.

pkgs/tools/text/sift/default.nix

···
     homepage = "https://sift-tool.org";
     maintainers = [ maintainers.carlsverre ];
     license = licenses.gpl3;
-    platforms = platforms.all;
+    platforms = platforms.linux;
   };
 }