A couple of fixes

- using LDFLAGS doesn't pull the required dependencies, move
  to using LOCAL_SHARED_LIBRARIES
- eliminate 'implicit declaration' warnings

Change-Id: I57f6feca6bfcf8b2e9d439462a33c9757cdde07d
Signed-off-by: Marcus Oakland <marcus.oakland@arm.com>
Signed-off-by: Kévin PETIT <kevin.petit@arm.com>