pkgbuilds/flutter/system-dart.patch

--- ./packages/flutter_tools/bin/tool_backend.dart.orig
+++ ./packages/flutter_tools/bin/tool_backend.dart
@@ -73,9 +73,9 @@
     exit(1);
   }
   final String flutterExecutable = pathJoin(<String>[
-    flutterRoot,
+    '/usr',
     'bin',
-    if (Platform.isWindows) 'flutter.bat' else 'flutter',
+    'flutter',
   ]);
   final String bundlePlatform = targetPlatform;
   final String target = '${buildMode}_bundle_${bundlePlatform}_assets';
--- ./packages/flutter_tools/bin/tool_backend.sh.orig
+++ ./packages/flutter_tools/bin/tool_backend.sh
@@ -3,7 +3,4 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.

-readonly flutter_bin_dir="${FLUTTER_ROOT}/bin"
-readonly dart_bin_dir="${flutter_bin_dir}/cache/dart-sdk/bin"
-
-exec "${dart_bin_dir}/dart" "${FLUTTER_ROOT}/packages/flutter_tools/bin/tool_backend.dart" "${@:1}"
+exec "${DART_ROOT:-"/opt/dart-sdk"}/bin/dart" "${FLUTTER_ROOT}/packages/flutter_tools/bin/tool_backend.dart" "${@:1}"
--- ./packages/flutter_tools/gradle/src/main/kotlin/FlutterPlugin.kt.orig
+++ ./packages/flutter_tools/gradle/src/main/kotlin/FlutterPlugin.kt
@@ -50,7 +50,7 @@
             addTaskForLockfileGeneration(rootProject)
         }
 
-        val flutterRootSystemVal: String? = System.getenv("FLUTTER_ROOT")
+        val flutterRootSystemVal: String? = System.getenv("FLUTTER_ROOT") ?: "/usr/bin/flutter"
         val flutterRootPath: String =
             resolveFlutterSdkProperty(flutterRootSystemVal)
                 ?: throw GradleException(
@@ -170,7 +170,7 @@
 
         val flutterExecutableName = getExecutableNameForPlatform("flutter")
         flutterExecutable =
-            Paths.get(flutterRoot!!.absolutePath, "bin", flutterExecutableName).toFile()
+            Paths.get("/usr", "bin", flutterExecutableName).toFile()
 
         // Validate that the provided Gradle, Java, AGP, and KGP versions are all within our
         // supported range.
--- ./packages/flutter_tools/lib/src/artifacts.dart.orig
+++ ./packages/flutter_tools/lib/src/artifacts.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.

+import 'dart:io' as io show Platform;
+
 import 'package:file/memory.dart';
 import 'package:meta/meta.dart';
 import 'package:process/process.dart';
@@ -1308,24 +1308,7 @@
   }
 
   String _getDartSdkPath() {
-    final String builtPath = _fileSystem.path.join(_hostEngineOutPath, 'dart-sdk');
-    if (_fileSystem.isDirectorySync(_fileSystem.path.join(builtPath, 'bin'))) {
-      return builtPath;
-    }
-
-    // If we couldn't find a built dart sdk, let's look for a prebuilt one.
-    final String prebuiltPath = _fileSystem.path.join(
-      _getFlutterPrebuiltsPath(),
-      _getPrebuiltTarget(),
-      'dart-sdk',
-    );
-    if (_fileSystem.isDirectorySync(prebuiltPath)) {
-      return prebuiltPath;
-    }
-
-    throwToolExit(
-      'Unable to find a built dart sdk at: "$builtPath" or a prebuilt dart sdk at: "$prebuiltPath"',
-    );
+    return io.Platform.environment['DART_ROOT'] ?? '/opt/dart-sdk';
   }
 
   String _getFlutterPrebuiltsPath() {
@@ -1382,7 +1343,7 @@

 /// Locate the Dart SDK.
 String _dartSdkPath(Cache cache) {
-  return cache.getRoot().childDirectory('dart-sdk').path;
+  return io.Platform.environment['DART_ROOT'] ?? '/opt/dart-sdk';
 }

 class _TestArtifacts implements Artifacts {
--- ./packages/flutter_tools/lib/src/cache.dart.orig
+++ ./packages/flutter_tools/lib/src/cache.dart
@@ -3,6 +3,7 @@
 // found in the LICENSE file.

 import 'dart:async';
+import 'dart:io' as io show Platform;

 import 'package:crypto/crypto.dart';
 import 'package:file/memory.dart';
@@ -421,8 +421,8 @@
 
   String get devToolsVersion {
     if (_devToolsVersion == null) {
-      const devToolsDirPath = 'dart-sdk/bin/resources/devtools';
-      final Directory devToolsDir = getCacheDir(devToolsDirPath, shouldCreate: false);
+      final String dartSdkRoot = io.Platform.environment['DART_ROOT'] ?? '/opt/dart-sdk';
+      final Directory devToolsDir = _fileSystem.directory(dartSdkRoot + '/bin/resources/devtools');
       if (!devToolsDir.existsSync()) {
         throw Exception('Could not find directory at ${devToolsDir.path}');
       }
--- ./packages/flutter_tools/lib/src/commands/create_base.dart.orig
+++ ./packages/flutter_tools/lib/src/commands/create_base.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.

+import 'dart:io' as io show Platform;
+
 import 'package:meta/meta.dart';
 import 'package:uuid/uuid.dart';

@@ -341,7 +341,7 @@
       'linuxIdentifier': linuxIdentifier,
       'windowsIdentifier': windowsIdentifier,
       'description': projectDescription,
-      'dartSdk': '$flutterRoot/bin/cache/dart-sdk',
+      'dartSdk': io.Platform.environment['DART_ROOT'] ?? '/opt/dart-sdk',
       'androidMinApiLevel': gradle.minSdkVersion,
       'androidSdkVersion': gradle.minSdkVersion,
       'pluginClass': pluginClass,
--- ./packages/flutter_tools/lib/src/dart/pub.dart.orig
+++ ./packages/flutter_tools/lib/src/dart/pub.dart
@@ -3,6 +3,7 @@
 // found in the LICENSE file.

 import 'dart:async';
+import 'dart:io' as io show Platform;

 import 'package:meta/meta.dart';
 import 'package:package_config/package_config.dart';
@@ -545,10 +546,7 @@
   List<String> _computePubCommand() {
     // TODO(zanderso): refactor to use artifacts.
     final String sdkPath = _fileSystem.path.joinAll(<String>[
-      Cache.flutterRoot!,
-      'bin',
-      'cache',
-      'dart-sdk',
+      io.Platform.environment['DART_ROOT'] ?? '/opt/dart-sdk',
       'bin',
       'dart',
     ]);
--- ./packages/flutter_tools/lib/src/dart/language_version.dart.orig
+++ ./packages/flutter_tools/lib/src/dart/language_version.dart
@@ -3,6 +3,7 @@
 // found in the LICENSE file.

 import 'dart:async';
+import 'dart:io' as io show Platform;

 import 'package:file/file.dart';
 import 'package:package_config/package_config.dart';
@@ -27,7 +27,7 @@
   // Either reading the file or parsing the version could fail on a corrupt Dart SDK.
   // let it crash so it shows up in crash logging.
   final File versionFile = fileSystem.file(
-    fileSystem.path.join(flutterRoot, 'bin', 'cache', 'dart-sdk', 'version'),
+    (io.Platform.environment['DART_ROOT'] ?? '/opt/dart-sdk') + '/version',
   );
   if (!versionFile.existsSync() && _inUnitTest()) {
     return LanguageVersion(2, 12);