dprint: installShellFiles when cross compiling (#422602)

pkgs/by-name/dp/dprint/package.nix

@@ -3,6 +3,7 @@
   stdenv,
   fetchFromGitHub,
   rustPlatform,
+  buildPackages,
   installShellFiles,
   writableTmpDirAsHomeHook,
   versionCheckHook,
@@ -26,9 +27,7 @@ rustPlatform.buildRustPackage (finalAttrs: {
   useFetchCargoVendor = true;
   cargoHash = "sha256-OnrsuVK1gEDweldq+P8lDkkrHjklsG8MRpM0wqWsdlM=";
 
-  nativeBuildInputs = lib.optionals (stdenv.buildPlatform.canExecute stdenv.hostPlatform) [
-    installShellFiles
-  ];
+  nativeBuildInputs = [ installShellFiles ];
 
   cargoBuildFlags = [
     "--package=dprint"
@@ -51,15 +50,20 @@ rustPlatform.buildRustPackage (finalAttrs: {
   ];
 
   postInstall =
+    let
+      dprint =
+        if stdenv.buildPlatform.canExecute stdenv.hostPlatform then
+          "$out/bin/dprint"
+        else
+          lib.getExe buildPackages.dprint;
+    in
     ''
       rm "$out/bin/test-process-plugin"
-    ''
-    + lib.optionalString (stdenv.buildPlatform.canExecute stdenv.hostPlatform) ''
       export DPRINT_CACHE_DIR="$(mktemp -d)"
       installShellCompletion --cmd dprint \
-        --bash <($out/bin/dprint completions bash) \
-        --zsh <($out/bin/dprint completions zsh) \
-        --fish <($out/bin/dprint completions fish)
+        --bash <(${dprint} completions bash) \
+        --zsh <(${dprint} completions zsh) \
+        --fish <(${dprint} completions fish)
     '';
 
   nativeInstallCheckInputs = [