Android: Update env variables and NDK preinstallation to match Godot buildsystem changes

[m4gr3d]

Update configuration based on the Android buildsystem change in godotengine/godot#44949.

[akien-mga]

The issue with this change is that I'll have to redownload the NDK every single time I do Android builds, which kind of defeats the purpose of using a pre-built container with all dependencies installed.

Moreover, this will fail building as I need the NDK to build the Mono runtimes in that same container build script.

[m4gr3d]

The issue with this change is that I'll have to redownload the NDK every single time I do Android builds, which kind of defeats the purpose of using a pre-built container with all dependencies installed.

Moreover, this will fail building as I need the NDK to build the Mono runtimes in that same container build script.

I've updated the changes based on your feedback. We will need to ensure the ANDROID_NDK_VERSION is updated to match the project's ndkVersion. On the other hand, we can also make it an argument as for the img_version and mono_version.

[akien-mga]

On the other hand, we can also make it an argument as for the img_version and mono_version.

It's fine hardcoded like done now IMO. It won't change often and it's not different from many other things hardcoded in build files like macOS and iOS SDK versions, etc.

[akien-mga]

Thanks!