fontmatrix: disable fortify hardening

pkgs/applications/graphics/fontmatrix/default.nix

···
 
   nativeBuildInputs = [ cmake ];
 
+  hardeningDisable = [ "format" ];
+
   meta = {
     description = "Fontmatrix is a free/libre font explorer for Linux, Windows and Mac";
     homepage = http://fontmatrix.be/;