USE="-arts" emerge sys-devel/icecream gives: checking for mcopidl... not found configure: error: The important program mcopidl was not found! Please check whether you installed aRts correctly or use --without-arts to compile without aRts support (this will remove functionality). The -arts USE flag should enable "--without-arts" at configure.
*** This bug has been marked as a duplicate of 126983 ***