Skip building cctools if host is not darwin
Skip building cctools if host is not darwin

braydonf/libstorj,Storj/libstorj-c,braydonf/libstorj-c,braydonf/libstorj,aleitner/libstorj-c,Storj/libstorj-c,braydonf/libstorj-c,aleitner/libstorj-c