[Xamarin.Android.Build.Tasks] fix InstallAndroidDependencies in .NET 8

[jonathanpeppers]

Fixes: https://dev.azure.com/devdiv/DevDiv/_workitems/edit/1837913

Testing on a DevBox with only the .NET 8 RC 1 SDK and dotnet workload install maui:

> dotnet new android
> dotnet build -t:InstallAndroidDependencies -p:AndroidSdkDirectory=C:\tools\android-sdk -p:JavaSdkDirectory=C:\tools\jdk -bl
Microsoft.Android.Sdk.Windows\34.0.0-rc.1.432\tools\Xamarin.Android.Common.Debugging.targets(110,2):
error XA5300:  The Android SDK directory could not be found. Check that the Android SDK Manager in Visual Studio shows a valid installation. To use a custom SDK path for a command line build, set the 'AndroidSdkDirectory' MSBuild property to the custom path.

Ok, that's completely broken... So let's try -c Release, as this target is related to Fast Deployment:

Microsoft.Android.Sdk.Windows\34.0.0-rc.1.432\tools\Xamarin.Android.Common.targets(664,2):
error : Could not locate Java 6 or 7 SDK.

I tested .NET 7 and it worked fine?!?

It turns out to be due to an additional _ResolveMonoAndroidSdks target running in .NET 8 that doesn't run in .NET 7:

https://github.com/xamarin/xamarin-android/blob/547a157a7aeae930e4fc6092636fa20771ff1ef6/src/Xamarin.Android.Build.Tasks/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.BuildOrder.targets#L181

This was introduced in dc3ccf2, but I don't think it is actually needed.

The GetAndroidDependencies target doesn't run during a normal build, so it doesn't seem like $(GetAndroidDependenciesDependsOn) should need to run anything extra either.

Let's see what CI says, but maybe we can just delete this line?

With this change in place, InstallAndroidDependencies works on my DevBox, and I'm also able to build apps in Debug and Release mode.

[dellis1972]

I can't remember if we have a DTB test which does not have a standard build first? I suspect that is where we might run into issues with the JavaPlatformPath not being set...

[jonathanpeppers]

There are a couple that just do design-time builds:

https://github.com/xamarin/xamarin-android/blob/547a157a7aeae930e4fc6092636fa20771ff1ef6/src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/IncrementalBuildTest.cs#L1179-L1193

https://github.com/xamarin/xamarin-android/blob/547a157a7aeae930e4fc6092636fa20771ff1ef6/src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/BuildTest2.cs#L693-L719