SDL_mixer: add a passthru.test and some words of caution

pkgs/by-name/sd/SDL_mixer/package.nix

@@ -10,6 +10,8 @@
   pkg-config,
   smpeg,
   stdenv,
+  # passthru.tests
+  onscripter-en,
   # Boolean flags
   enableNativeMidi ? false,
   enableSdltest ? (!stdenv.hostPlatform.isDarwin),
@@ -20,6 +22,9 @@ stdenv.mkDerivation (finalAttrs: {
   pname = "SDL_mixer";
   version = "1.2.12";
 
+  # word of caution: while there is a somewhat maintained SDL-1.2 branch on
+  # https://github.com/libsdl-org/SDL_mixer, it switches from smpeg to mpg123 which
+  # breaks autoconf in a bunch of packages, it's better to cherry-pick patches as needed
   src = fetchurl {
     url = "http://www.libsdl.org/projects/SDL_mixer/release/SDL_mixer-${finalAttrs.version}.tar.gz";
     hash = "sha256-FkQwgnmpdXmQSeSCavLPx4fK0quxGqFFYuQCUh+GmSo=";
@@ -102,6 +107,10 @@ stdenv.mkDerivation (finalAttrs: {
 
   strictDeps = true;
 
+  passthru.tests = {
+    inherit onscripter-en;
+  };
+
   meta = {
     description = "SDL multi-channel audio mixer library";
     homepage = "http://www.libsdl.org/projects/SDL_mixer/";