Set LOCAL_SDK_VERSION on pdk/apps/HelloPDK/jni

libhellojni_jni, referred by app HelloPDK, is a simple stub library and
does not use any platform API. HelloPDK has been built with SDK, so this
causes link-type check warnings. LOCAL_SDK_VERSION is added to
libhellojni_jni in order to remove warning.

Bug: 73907534
Test: mma -j does not show any link-type warnings
Change-Id: I188dfe9a46aedf905d2b804040bf2ad75f212b38