Apply the same Nix lipo workaround to iOS

hook/build.dart

@@ -28,11 +28,7 @@ Future<void> main(List<String> args) => build(args, (input, output) async {
       final iosConfig = codeConfig.iOS;
       iosSdk = iosConfig.targetSdk;
       final minVersion = iosConfig.targetVersion;
-      iosSdkPath = (await Process.run("xcrun", [
-        "--sdk",
-        iosSdk.type,
-        "--show-sdk-path",
-      ])).stdout.toString().trim();
+      iosSdkPath = await getXCodeSDK(sdkType: iosSdk.type);
       final archTriple = switch (targetArch) {
         Architecture.arm64 => "arm64",
         Architecture.x64 => "x86_64",
@@ -45,12 +41,7 @@ Future<void> main(List<String> args) => build(args, (input, output) async {
           : "$archTriple-apple-ios$minVersion.0";
       extraEnv = {
         "GOOS": "ios",
-        "CC": (await Process.run("xcrun", [
-          "--sdk",
-          iosSdk.type,
-          "-f",
-          "clang",
-        ])).stdout.toString().trim(),
+        "CC": await getXCodeClang(sdkType: iosSdk.type),
         "CGO_CFLAGS": "-isysroot $iosSdkPath -target $iosTargetTriple",
         "CGO_LDFLAGS": "-isysroot $iosSdkPath -target $iosTargetTriple",
       };

ios/Runner.xcodeproj/project.pbxproj

@@ -336,7 +336,7 @@
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 			shellPath = /bin/sh;
-			shellScript = "/bin/sh \"$FLUTTER_ROOT/packages/flutter_tools/bin/xcode_backend.sh\" embed_and_thin";
+			shellScript = "export PATH=\"$PROJECT_DIR/scripts:$PATH\"\n/bin/sh \"$FLUTTER_ROOT/packages/flutter_tools/bin/xcode_backend.sh\" embed_and_thin";
 		};
 		9740EEB61CF901F6004384FC /* Run Script */ = {
 			isa = PBXShellScriptBuildPhase;
@@ -351,7 +351,7 @@
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 			shellPath = /bin/sh;
-			shellScript = "/bin/sh \"$FLUTTER_ROOT/packages/flutter_tools/bin/xcode_backend.sh\" build";
+			shellScript = "export PATH=\"$PROJECT_DIR/scripts:$PATH\"\n/bin/sh \"$FLUTTER_ROOT/packages/flutter_tools/bin/xcode_backend.sh\" build";
 		};
 		EE82EC529EB6C0F1FA480659 /* [CP] Check Pods Manifest.lock */ = {
 			isa = PBXShellScriptBuildPhase;

ios/scripts/lipo

@@ -0,0 +1,15 @@
+#!/bin/sh
+# Workaround for NixOS/nixpkgs#405066: frameworks copied from the Nix store
+# stay read-only, so lipo can't write its temporary output file when Flutter
+# thins them during the build. Make the framework writable before delegating
+# to the real lipo.
+for arg in "$@"; do
+  case "$arg" in
+    */*.framework/*)
+      fw_dir="${arg%.framework/*}.framework"
+      chmod -R +w "$fw_dir" 2>/dev/null
+      ;;
+  esac
+done
+
+exec /usr/bin/lipo "$@"

lib/helpers/extensions/get_xcode_sdk.dart

@@ -1,11 +1,22 @@
 import "dart:io";
 
-Future<String> getXCodeSDK() async {
-  final result = await Process.run("xcrun", ["--show-sdk-path"]);
+Future<String> _runXcrun(List<String> args, String errorContext) async {
+  final result = await Process.run("xcrun", args);
 
   if (result.exitCode != 0) {
-    throw Exception("Failed to get XCode SDK\n${result.stderr}");
+    throw Exception("Failed to $errorContext\n${result.stderr}");
   }
 
-  return result.stdout.trim();
+  return result.stdout.toString().trim();
 }
+
+Future<String> getXCodeSDK({String? sdkType}) => _runXcrun([
+  if (sdkType != null) ...["--sdk", sdkType],
+  "--show-sdk-path",
+], "get XCode SDK");
+
+Future<String> getXCodeClang({String? sdkType}) => _runXcrun([
+  if (sdkType != null) ...["--sdk", sdkType],
+  "-f",
+  "clang",
+], "get XCode clang");