external: don't display object during make clean
external: don't display object during make clean

Change-Id: I9defe814b5e01164b5625dafe933189d451bfad2
Signed-off-by: Byoungtae Cho <d399e7ab5fdc23c09a148b7028e772c5bd5c24c5@samsung.com>

JunhwanPark/TizenRT,JunhwanPark/TizenRT,JunhwanPark/TizenRT,JunhwanPark/TizenRT,JunhwanPark/TizenRT,JunhwanPark/TizenRT