meson: enable auto_features by default

We disabled them by default when they were introduced in

https://github.com/NixOS/nixpkgs/pull/42994

but enabling them probably makes more sense:

https://github.com/NixOS/nixpkgs/pull/54398
https://github.com/NixOS/nixpkgs/pull/63491

pkgs/development/tools/build-managers/meson/setup-hook.sh

@@ -17,7 +17,7 @@ mesonConfigurePhase() {
         --includedir=${!outputInclude}/include \
         --mandir=${!outputMan}/share/man --infodir=${!outputInfo}/share/info \
         --localedir=${!outputLib}/share/locale \
-        -Dauto_features=disabled \
+        -Dauto_features=${mesonAutoFeatures:-enabled} \
         $mesonFlags"
 
     mesonFlags="${crossMesonFlags+$crossMesonFlags }--buildtype=${mesonBuildType:-release} $mesonFlags"