AGP8 mandates build.gradle to add namespace

[wyq0918dev]

Add the following code in android{} of build.gradle

// Conditional for compatibility with AGP <4.2.
if (project.android.hasProperty("namespace")) {
    namespace 'com.example.flutter_pty'
}

[shadow3aaa]

Since this repo seems no longer being maintained, you can use this fork instead to fix this issue

dependencies:
// ...
  flutter_pty:
    git: https://github.com/shadow3aaa/flutter_pty