Fix dependency offset for propagated gcc

examples/cross-aarch64/shell.nix

@@ -1,18 +1,22 @@
-with import <nixpkgs> {
+(import <nixpkgs> {
   crossSystem = "aarch64-linux";
   overlays = [ (import ../..) ];
-};
+}).callPackage (
+{ mkShell, rust-bin, pkg-config, openssl, pkgsBuildBuild }:
 mkShell {
   nativeBuildInputs = [
     # Manual `buildPackages` is required here. See: https://github.com/NixOS/nixpkgs/issues/49526
     # build = host = x86_64, target = aarch64
-    buildPackages.rust-bin.stable.latest.minimal
-    buildPackages.pkg-config
-    # build = host = target = x86_64, just to avoid re-build.
+    rust-bin.stable.latest.minimal
+    pkg-config
+
+    # build = host = target = x86_64
+    # qemu itself is multi-platform and `target` doesn't matter for it.
+    # Use build system's to avoid rebuild.
     pkgsBuildBuild.qemu
   ];
   buildInputs = [
     # build = x86_64, host = target = aarch64
     openssl
   ];
-}
+}) {}

rust-overlay.nix

@@ -326,10 +326,9 @@ let
 
       # FIXME: If these propagated dependencies go components, darwin build will fail with "`-liconv` not found".
 
-      # use propagatedNativebuildinputs here because we want these dependencies to end up
-      # as buildPlatform dependencies on the derivation using the compiler even though
-      # they are targetPlatform dependencies from the compiler's perspective
-      propagatedNativeBuildInputs = [ self.stdenv.cc self.targetPackages.stdenv.cc ] ++
+      # Ourselves have offset -1. In order to make these offset -1 dependencies of downstream derivation,
+      # they are offset 0 propagated.
+      propagatedBuildInputs = [ self.gcc self.buildPackages.gcc ] ++
         self.lib.optional (self.stdenv.targetPlatform.isDarwin) self.targetPackages.libiconv;
 
       meta.platforms = self.lib.platforms.all;