Fix target_link_libraries in setup_arduino_library()

Newer versions of cmake (2.8.12 and later) warn about
policy CMP0022 (and CMP0038) regarding self-linking targets.
Removing ${LIB_TARGETS} from the inner target_link_libraries()
call fixes this.

Signed-off-by: Chris Evich <chris-arduino@anonomail.me>