Fix aar rules

aar files should build to the module out directory, not the root of
the out directory.  Also give the rules a description so they get a
better status line.

Test: m out/soong/.intermediates/frameworks/base/packages/SystemUI/SystemUI-core/android_common/SystemUI-core.aar
Change-Id: Ie8de0421427985c466d909f83c8e0146f7e0bea8

java/app_builder.go

@@ -122,9 +122,10 @@ func BuildAAR(ctx android.ModuleContext, outputFile android.WritablePath,
 	}
 
 	ctx.Build(pctx, android.BuildParams{
-		Rule:      buildAAR,
-		Implicits: deps,
-		Output:    outputFile,
+		Rule:        buildAAR,
+		Description: "aar",
+		Implicits:   deps,
+		Output:      outputFile,
 		Args: map[string]string{
 			"manifest":   manifest.String(),
 			"classesJar": classesJarPath,