Problem with freezed / build_runner in plain dart package: "dart run" command not available

Question

I am trying to use the freezed package inside a plain dart package - NO flutter!

I am following the instructions at https://pub.dev/packages/freezed#run-the-generator .

My pubspec.yaml:

...
version: 1.0.0
# homepage: https://www.example.com
environment:
  sdk: '>=2.17.5 <3.0.0'

dependencies:
  bloc: ^8.0.3
  freezed_annotation: ^2.1.0

dev_dependencies:
  build_runner: ^2.2.0
  freezed: ^2.1.0+1
  lints: ^2.0.0
  mockito: ^5.3.0
  test: ^1.16.0

My example class:

import 'package:freezed_annotation/freezed_annotation.dart';

part 'person.freezed.dart';

@freezed
class Person with _$Person {
  const factory Person({
    required String firstName,
    required String lastName,
  }) = _Person;
}

But when I call

dart run build_runner build

I get the following error:

Unhandled exception:
Could not load "file:///{my_project_path}/run": FileSystemException: Cannot open file, path = '{my_project_path}//run' (OS Error: No such file or directory, errno = 2)
null

The same result when I use the run build command from the freezed vs code extension:

Running `dart run build_runner build --delete-conflicting-outputs`
Current working folder: `{my_project_path}`

Unhandled exception:
Could not load "file:///{my_project_path}/run": FileSystemException: Cannot open file, path = '{my_project_path}/run' (OS Error: No such file or directory, errno = 2)
null

So I created a flutter package instead with the same dependencies and class and when I now call

flutter pub run build_runner build

it works!

My dart version:

% dart --version                    
Dart VM version: 1.24.3 (Wed Dec 13 23:26:59 2017) on "macos_x64"

OS: macOS Big Sur Version 11.6.7

And yes, I googled the problem extensively, but did not find anything related!

Any suggestions? Anyone? Please!

Edit:

Seems that my standalone dart installation is seriously broken. I can call dart my_dart_program.dart and it works. But if I try to call any dart commands like create, run, ... it looks for a file with this name in the current directory.

I changed my path settings to always use the dart version shipped with flutter and everything works just fine.

So I don't use the latest stable of dart for my dart only code, but I always know that everything is compatible with the current flutter version.