fltrdr: enable darwin support (#517258)

pkgs/tools/misc/fltrdr/default.nix

@@ -25,6 +25,10 @@ stdenv.mkDerivation rec {
     openssl
   ];
 
+  postPatch = lib.optionalString stdenv.isDarwin ''
+    sed -i '/stdc++fs/d' CMakeLists.txt
+  '';
+
   meta = {
     homepage = "https://octobanana.com/software/fltrdr";
     description = "TUI text reader for the terminal";
@@ -39,7 +43,7 @@ stdenv.mkDerivation rec {
       setting.
     '';
 
-    platforms = lib.platforms.linux; # can only test linux
+    platforms = lib.platforms.linux ++ lib.platforms.darwin;
     license = lib.licenses.mit;
     maintainers = [ lib.maintainers.matthiasbeyer ];
     mainProgram = "fltrdr";