[dartdev] `dart run` ignores `-D` due to kernel caching

[dcharkes]

Consider:

# bin/my_app.dart

void main() {
  const foo = const String.fromEnvironment('foo', defaultValue: 'no foo');
  print(foo);
}

Passing a full script path works as expected

$ dart -Dfoo=foo run bin/my_app.dart 
foo
$ dart -Dfoo=bar run bin/my_app.dart 
bar
$ dart run -Dfoo=foo bin/my_app.dart 
foo
$ dart run -Dfoo=bar bin/my_app.dart 
bar

However, using just the name instead of the full path uses caching, and ignores the defines:

$ dart -Dfoo=foo run my_app
foo
$ dart -Dfoo=bar run my_app
foo