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
diff --git a/java/aar.go b/java/aar.go
index a108ba0..d08e487 100644
--- a/java/aar.go
+++ b/java/aar.go
@@ -332,7 +332,7 @@
 
 	a.Module.compile(ctx, a.aaptSrcJar)
 
-	a.aarFile = android.PathForOutput(ctx, ctx.ModuleName()+".aar")
+	a.aarFile = android.PathForModuleOut(ctx, ctx.ModuleName()+".aar")
 	var res android.Paths
 	if a.androidLibraryProperties.BuildAAR {
 		BuildAAR(ctx, a.aarFile, a.outputFile, a.manifestPath, a.rTxt, res)