Fix cross-compilation for fwupd (#351182)

pkgs/by-name/fw/fwupd/build-time-python.nix

@@ -0,0 +1,26 @@
+# Python environment that needs to be able to run the following:
+# https://github.com/fwupd/fwupd/blob/f8b5ed554ce3d5e7a016e6e97f0a03e48e510ddb/plugins/uefi-capsule/meson.build#L73
+
+{
+  lib,
+  glib,
+  pango,
+  python3,
+  harfbuzz,
+}:
+
+let
+  giTypelibPath = lib.makeSearchPathOutput "out" "lib/girepository-1.0" [
+    harfbuzz
+    pango
+    glib
+  ];
+in
+(python3.withPackages (p: [
+  p.jinja2
+  p.pygobject3
+  p.setuptools
+])).override
+  {
+    makeWrapperArgs = [ "--set GI_TYPELIB_PATH ${giTypelibPath}" ];
+  }

pkgs/by-name/fw/fwupd/package.nix

@@ -1,6 +1,7 @@
 # Updating? Keep $out/etc synchronized with passthru keys
 
 {
+  pkgsBuildBuild,
   stdenv,
   lib,
   fetchFromGitHub,
@@ -22,6 +23,7 @@
   elfutils,
   valgrind,
   meson,
+  mesonEmulatorHook,
   libuuid,
   ninja,
   gnutls,
@@ -57,14 +59,6 @@
 }:
 
 let
-  python = python3.withPackages (
-    p: with p; [
-      jinja2
-      pygobject3
-      setuptools
-    ]
-  );
-
   isx86 = stdenv.hostPlatform.isx86;
 
   # Dell isn't supported on Aarch64
@@ -165,30 +159,39 @@ stdenv.mkDerivation (finalAttrs: {
     ./efi-app-path.patch
   ];
 
-  nativeBuildInputs = [
-    # required for firmware zipping
-    ensureNewerSourcesForZipFilesHook
-    meson
-    ninja
-    gi-docgen
-    pkg-config
-    gobject-introspection
-    gettext
-    shared-mime-info
-    valgrind
-    gnutls
-    protobufc # for protoc
-    python
-    wrapGAppsNoGuiHook
-    vala
+  strictDeps = true;
+
+  depsBuildBuild = [
+    pkg-config # for finding build-time dependencies
+    (pkgsBuildBuild.callPackage ./build-time-python.nix { })
   ];
 
   propagatedBuildInputs = [
     json-glib
   ];
 
+  nativeBuildInputs =
+    [
+      ensureNewerSourcesForZipFilesHook # required for firmware zipping
+      meson
+      ninja
+      pkg-config
+      gettext
+      shared-mime-info
+      valgrind
+      protobufc # for protoc
+      wrapGAppsNoGuiHook
+      vala
+      gobject-introspection
+      gi-docgen
+    ]
+    ++ lib.optionals (!stdenv.buildPlatform.canExecute stdenv.hostPlatform) [
+      mesonEmulatorHook
+    ];
+
   buildInputs =
     [
+      gnutls
       polkit
       libxmlb
       gusb