Fix for ettercap 0.8.1 lua cmake error on osx 10.10 (Hack)

This is a small hack for fixing lua cmake error on OS X 10.10 Yosemite.

like this :
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CMake Error at src/CMakeLists.txt:191 (SET_TARGET_PROPERTIES):
  set_target_properties Can not find target to add properties to: ettercap
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http://pastebin.com/WS9wwuKj