ocamlyices2: ext/Makefile: fix libyices re-configured on each make
ocamlyices2: ext/Makefile: fix libyices re-configured on each make

polazarus/ocamlyices2,maelvalais/ocamlyices2,maelvalais/ocamlyices2,maelvalais/ocamlyices2,polazarus/ocamlyices2,polazarus/ocamlyices2,maelvalais/ocamlyices2,polazarus/ocamlyices2