sic: fix cross-compilation

pkgs/applications/networking/irc/sic/default.nix

···
   pname = "sic";
   version = "1.2";
 
-  makeFlags = [ "PREFIX=$(out)" ];
   src = fetchurl {
     url = "https://dl.suckless.org/tools/sic-${version}.tar.gz";
     sha256 = "ac07f905995e13ba2c43912d7a035fbbe78a628d7ba1c256f4ca1372fb565185";
   };
+
+  makeFlags = [ "CC:=$(CC)" ];
+
+  installFlags = [ "PREFIX=$(out)" ];
 
   meta = {
     description = "Simple IRC client";