Replace Launcher2 by Launcher3 for SDK system images

Launcher2 is deprecated and should use Launcher3, as the latter
can handle higher resolution devices (such as Nexus 6).

Change-Id: I5215d87f8536869486bb0b6317ae382a21099925
diff --git a/target/product/sdk_base.mk b/target/product/sdk_base.mk
index 0fa6e08..ee54700 100644
--- a/target/product/sdk_base.mk
+++ b/target/product/sdk_base.mk
@@ -27,6 +27,7 @@
 	Fallback \
 	Gallery \
 	GestureBuilder \
+	Launcher3 \
 	LegacyCamera \
 	librs_jni \
 	libwnndict \