fix cross-compiled builds

default.nix

@@ -1,4 +1,4 @@
-{ system ? builtins.currentSystem, git_version ? "unknown", }:
+{ system ? builtins.currentSystem, git_version ? null, }:
 
 with import ./nix/common.nix;
 

nix/compile.nix

@@ -29,6 +29,11 @@ let
     "arm-unknown-linux-musleabihf" = "ARM_UNKNOWN_LINUX_MUSLEABIHF";
   };
 
+  pkgsNative = import nixpkgs {
+    inherit system;
+    overlays = [ (import rust-overlay) ];
+  };
+
   pkgs = if target != null then
     import nixpkgs {
       inherit system;
@@ -39,10 +44,7 @@ let
       overlays = [ (import rust-overlay) ];
     }
   else
-    import nixpkgs {
-      inherit system;
-      overlays = [ (import rust-overlay) ];
-    };
+    pkgsNative;
 
   inherit (pkgs) lib stdenv;
 
@@ -115,14 +117,13 @@ let
       strictDeps = true;
       cargoExtraArgs = "--locked --features ${featuresStr}";
 
-      nativeBuildInputs = with pkgs; ([
-        pkg-config
-        stdenv.cc
-        protobuf
+      nativeBuildInputs = [
+        pkgsNative.protobuf
+        pkgs.stdenv.cc
       ] ++ lib.optionals (target == null) [
-        clang
-        mold
-      ]);
+        pkgs.clang
+        pkgs.mold
+      ];
 
       CARGO_PROFILE = if release then "release" else "dev";
       CARGO_BUILD_RUSTFLAGS =