gpac: add support for darwin

The cctools dependency is needed for libtool[^1], while the Carbon
dependency comes from carbon_hook.c[^2].

[^1]: https://github.com/gpac/gpac/blob/df8121066cf8fb25cc70adf7ca8b35bda82fe216/src/Makefile#L377
[^2]: https://github.com/gpac/gpac/blob/df8121066cf8fb25cc70adf7ca8b35bda82fe216/applications/gpac/carbon_hook.c#L36.

pkgs/applications/video/gpac/default.nix

@@ -1,4 +1,4 @@
-{ lib, stdenv, fetchFromGitHub, pkg-config, zlib }:
+{ lib, stdenv, fetchFromGitHub, cctools, pkg-config, Carbon, zlib }:
 
 stdenv.mkDerivation rec {
   pname = "gpac";
@@ -13,9 +13,17 @@ stdenv.mkDerivation rec {
 
   # this is the bare minimum configuration, as I'm only interested in MP4Box
   # For most other functionality, this should probably be extended
-  nativeBuildInputs = [ pkg-config ];
+  nativeBuildInputs = [
+    pkg-config
+  ] ++ lib.optionals stdenv.isDarwin [
+    cctools
+  ];
 
-  buildInputs = [ zlib ];
+  buildInputs = [
+    zlib
+  ] ++ lib.optionals stdenv.isDarwin [
+    Carbon
+  ];
 
   enableParallelBuilding = true;
 
@@ -36,6 +44,6 @@ stdenv.mkDerivation rec {
     homepage = "https://gpac.wp.imt.fr";
     license = licenses.lgpl21;
     maintainers = with maintainers; [ bluescreen303 mgdelacroix ];
-    platforms = platforms.linux;
+    platforms = platforms.unix;
   };
 }

pkgs/top-level/all-packages.nix

@@ -20963,7 +20963,10 @@ with pkgs;
     autoconf = buildPackages.autoconf269;
   };
 
-  gpac = callPackage ../applications/video/gpac { };
+  gpac = callPackage ../applications/video/gpac {
+    inherit (darwin) cctools;
+    inherit (darwin.apple_sdk.frameworks) Carbon;
+  };
 
   gpgme = callPackage ../development/libraries/gpgme { };