Flutter build fails on WSL2 with FileSystemException (OS Error: Cannot allocate memory, errno = 12)

I had the same error on WSL1 and it looks like a Dart runtime bug (not confirmed). I don't have a real solution but here is how I worked around:

1. Go to your Flutter installation directory.

2. Modify packages/flutter_tools/lib/src/build_system/targets/assets.dart as follows (convert Future.wait(Iterable<Future>) into a plain for loop):

   diff --git a/packages/flutter_tools/lib/src/build_system/targets/assets.dart b/packages/flutter_tools/lib/src/build_system/targets/assets.dartindex 83684e4455..b0bb340a79 100644--- a/packages/flutter_tools/lib/src/build_system/targets/assets.dart+++ b/packages/flutter_tools/lib/src/build_system/targets/assets.dart@@ -86,8 +86,7 @@ Future<Depfile> copyAssets(Environment environment, Directory outputDirectory, {      kSkSLShaderBundlePath: skslBundle,   };-  await Future.wait<void>(-    assetEntries.entries.map<Future<void>>((MapEntry<String, DevFSContent> entry) async {+  for (final MapEntry<String, DevFSContent> entry in assetEntries.entries) {      final PoolResource resource = await pool.request();      try {         // This will result in strange looking files, for example files with `/`@@ -115,7 +114,7 @@ Future<Depfile> copyAssets(Environment environment, Directory outputDirectory, {      } finally {         resource.release();      }-  }));+  }   // Copy deferred components assets only for release or profile builds.   // The assets are included in assetBundle.entries as a normal asset when

3. Remove bin/cache/flutter_tools.snapshot to force the Flutter Tools snapshot to be re-generated.

4. Try flutter build or flutter run again.