prepare-detached-build in ExpoKit android build on windows

Hey there!

we recently ejected to ExpoKit (will switch to bare workflow once possible). Some colleagues work on windows and had problems getting started. First of all we had to add the gradlew.bat manually. Second of all the windows build never updated DetachBuildConstants.java with the current development URL.

Looking at https://github.com/expo/expo/blob/master/android/app/expo.gradle#L18-L22 I see that expo prepare-detached-build is only performed for non-windows builds. I wonder if there’s a reason for that. We changed

commandLine "cmd", "/c", ".\\node_modules\\expokit\\detach-scripts\\run-exp.bat"

to

commandLine "cmd", "/c", ".\\node_modules\\expokit\\detach-scripts\\run-exp.bat", "prepare-detached-build", "--platform", "android", expoRoot

and it’s working for us now. Should this be considered a bug?