[Xamarin.Android.Build.Tasks] AndroidJavaSource refs dependent jars (#8194)

Fixes: #8191

The implementation of `@(AndroidJavaSource)` was missing one component:
if your project contains `@(PackageReference)`s to NuGet packages which
pull in `.jar` files, those `.jar` files would *not* be referenced when
building `@(AndroidJavaSource)`.

For example, if you reference the [Xamarin.AndroidX.AppCompat][0]
package, there is an expectation that `@(AndroidJavaSource)` code
should be able to use the type `androidx.appcompat.widget.Toolbar`.

Unfortunately, this would fail:

	Error	JAVAC0000	 error: package androidx.appcompat.widget does not exist

This would fail because the `javac` invocation was missing references
to the `classes.jar` files which are extracted into the
`$(IntemediateOutputPath)lp` directory.

Update the (internal) `$(_CompileBindingJavaDependsOnTargets)` property
so that the `_GetLibraryImports` target is a dependency.  This will
call the chain of targets which extracts the dependent `classes.jar`
files and populates the `@(Jars)` ItemGroup which is used in the
`_CompileBindingJava` target.  This should allow users to write simple
wrapper methods in Java that wrap more complex APIs.

[0]: https://www.nuget.org/packages/Xamarin.AndroidX.AppCompat/1.1.0.1

Author: dellis1972

src/Xamarin.Android.Build.Tasks/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.BuildOrder.targets

@@ -187,6 +187,7 @@ properties that determine build ordering.
     </_ResolveLibraryProjectsDependsOn>
     <_CompileBindingJavaDependsOnTargets>
       _AdjustJavacVersionArguments;
+      _GetLibraryImports;
       _DetermineBindingJavaLibrariesToCompile;
       _GetJavaPlatformJar;
     </_CompileBindingJavaDependsOnTargets>

src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/BuildTest.cs

@@ -1554,6 +1554,35 @@ public void CheckLintConfigMerging ()
 			}
 		}
 
+		[Test]
+		public void BuildApplicationWithJavaSourceUsingAndroidX ([Values(true, false)] bool isRelease)
+		{
+			var proj = new XamarinAndroidApplicationProject () {
+				IsRelease = isRelease,
+				OtherBuildItems = {
+					new BuildItem (AndroidBuildActions.AndroidJavaSource, "ToolbarEx.java") {
+						TextContent = () => @"package com.unnamedproject.unnamedproject;
+import android.content.Context;
+import androidx.appcompat.widget.Toolbar;
+public class ToolbarEx {
+	public static Toolbar GetToolbar (Context context) {
+		return new Toolbar (context);
+	}
+}
+",
+						Encoding = Encoding.ASCII
+					},
+				}
+			};
+			proj.PackageReferences.Add (KnownPackages.AndroidXAppCompat);
+			using (var b = CreateApkBuilder ()) {
+				b.ThrowOnBuildFailure = false;
+				Assert.IsTrue (b.Build (proj), "Build should have succeeded");
+
+				Assert.IsTrue (b.Clean (proj), "Clean should have succeeded.");
+			}
+		}
+
 		[Test]
 		public void BuildApplicationCheckThatAddStaticResourcesTargetDoesNotRerun ()
 		{