Code segments generator has different output for unix and macOS

See the transformations demo.

In the subsegment transformationsDemo#2 we have the imports and these are the outputs generated on a macOS system:

import 'dart:collection' show IterableMixin;
import 'dart:math';
import 'dart:ui' show Vertices;
import 'package:flutter/material.dart' hide Gradient;
import 'package:vector_math/vector_math_64.dart' show Vector3;

In the subsegment transformationsDemo#3 we have the imports and theser are the outputs generated on Ubuntu:

import 'package:flutter/material.dart';
import 'package:vector_math/vector_math_64.dart' show Vector3;
import 'transformations_demo_inertial_motion.dart';

Verify l10n has different output on Windows

To be debugged.

Migrated from material-components/material-components-flutter-gallery#565