Don't build the stub org.apache.http.legacy.jar in PDK build.

Change-Id: Iaacafbacba49c233f9a3859382b93f27e6d6773d
diff --git a/Android.mk b/Android.mk
index 7bfe9bb..f44b4d4 100644
--- a/Android.mk
+++ b/Android.mk
@@ -114,7 +114,7 @@
 apache_http_stubs_gen_stamp := $(full_target)
 
 # For unbundled build we'll use the prebuilt jar from prebuilts/sdk.
-ifeq (,$(TARGET_BUILD_APPS))
+ifeq (,$(TARGET_BUILD_APPS)$(filter true,$(TARGET_BUILD_PDK)))
 ###############################################
 # Build the stub source files into a jar.
 include $(CLEAR_VARS)