$ ocamlopt -verbose -I lwt -I ubase -o unison unix.cmxa str.cmxa -cclib -lutil ubase/projectInfo.cmx osxsupport.o pty.o + gcc -o unison -I/usr/lib/ocaml /tmp/.private/shalupov/camlstartupec6215.o /usr/lib/ocaml/std_exit.o linktext.o /usr/lib/ocaml/str.a /usr/lib/ocaml/unix.a /usr/lib/ocaml/stdlib.a -Llwt -Lubase -L/usr/lib/ocaml -lstr -lunix -lutil osxsupport.o pty.o /usr/lib/ocaml/libasmrun.a -lm -ldl pty.o: In function `c_openpty':pty.c:(.text+0x67): undefined reference to `openpty'