Makefile: installopt enhancement
Makefile: installopt enhancement

If appropriate, install flexdll/flexlink.opt as
$(INSTALL_BINDIR)/flexlink$(EXE). This will not happen under Unix where
flexlink is not compiled but makes this target identical to its Windows
counterpart.

gerdstolpmann/ocaml,gerdstolpmann/ocaml,gerdstolpmann/ocaml,gerdstolpmann/ocaml,gerdstolpmann/ocaml