cmake DUNE_SYS_HAS_LIB_PHIDGET21 examples

LSTS/dune cmake/Libraries/Phidget.cmake :36 

else(DUNE_SYS_HAS_LIB_PHIDGET21 AND DUNE_SYS_HAS_PHIDGET21_H)

LSTS/dune cmake/Libraries/Phidget.cmake :39 

endif(DUNE_SYS_HAS_LIB_PHIDGET21 AND DUNE_SYS_HAS_PHIDGET21_H)