Add gcc-tune script

pkgs/default.nix

@@ -10,6 +10,7 @@ in
   aacs = c ./aacs.nix { };
   brew = c ./homebrew.nix { };
   create_ssl = c ./create_ssl.nix { };
+  gcc-tune = c ./gcc-tune.nix { };
   gen-build = c ./gen-build { };
   hms = c ./hms { };
   inject-darwin = c ./inject-darwin.nix { };

pkgs/gcc-tune.nix

@@ -0,0 +1,16 @@
+{
+  writeShellApplication,
+  gcc,
+  gnugrep,
+}:
+
+writeShellApplication {
+  name = "gcc-tune";
+  runtimeInputs = [
+    gcc
+    gnugrep
+  ];
+  text = ''
+    gcc -march=native -Q --help=target | grep 'mtune='
+  '';
+}