The Android NDK guide explains the two variables in the Adnroid.mk
as follows:
LOCAL_LDLIBS - The list of additional linker flags to be used
It is possible that there is not a functional difference at the present time (or that this is a minor mistake in the documentation) but the intent (in accordance with longstanding tradition of naming variables of this type) is that:
LOCAL_LDLIBS would specify libraries or at least objects to be linked into the result
LOCAL_LDFLAGS would specify other configuration options to the linker