orca: fix cross-compiled builds (#453917)

pkgs/by-name/or/orca/package.nix

@@ -1,5 +1,7 @@
 {
   lib,
+  stdenv,
+  buildPackages,
   pkg-config,
   fetchurl,
   meson,
@@ -47,7 +49,15 @@ python3.pkgs.buildPythonApplication rec {
     })
   ];
 
+  # needed for cross-compilation
+  depsBuildBuild = [ pkg-config ];
+
   nativeBuildInputs = [
+    # cross-compilation support requires the host environment's build time
+    # to make the following buildPackages available.
+    buildPackages.gtk3
+    buildPackages.python3
+    buildPackages.python3Packages.pygobject3
     meson
     ninja
     wrapGAppsHook3
@@ -84,6 +94,11 @@ python3.pkgs.buildPythonApplication rec {
     gst_all_1.gst-plugins-good
   ];
 
+  # Help GI find typelibs during Meson's configure step in cross builds
+  preConfigure = lib.optionalString (stdenv.buildPlatform != stdenv.hostPlatform) ''
+    export GI_TYPELIB_PATH=${buildPackages.gtk3}/lib/girepository-1.0''${GI_TYPELIB_PATH:+:$GI_TYPELIB_PATH}
+  '';
+
   dontWrapGApps = true; # Prevent double wrapping
 
   preFixup = ''