Add # apex symbols.

Bug: 120637510
Test: manually verify APEX symbols aren't in the NDK stub
m libbinder_ndk libbinder_ndk.ndk.Q libbinder_ndk.ndk.current
readelf -Ws $ANDROID_PRODUCT_OUT/obj/SHARED_LIBRARIES/libbinder_ndk.ndk.Q_intermediates/libbinder_ndk.so | grep AServiceManager
< command failed >
readelf -Ws $ANDROID_PRODUCT_OUT/obj/SHARED_LIBRARIES/libbinder_ndk.ndk.current_intermediates/libbinder_ndk.so | grep AServiceManager
< command failed >
readelf -Ws $ANDROID_PRODUCT_OUT/obj/SHARED_LIBRARIES/libbinder_ndk_intermediates/libbinder_ndk.so | grep AServiceManager_getService
   261: 000000000000ede8   244 FUNC    GLOBAL DEFAULT   14 AServiceManager_getService

Change-Id: I9377c72c30fbad5993d580506ed5a061f78e81b6