Add dependency from syncterm.c -> ciolib so rgbmap.h can be created

src/syncterm/extdeps.mk

 $(MTOBJODIR)$(DIRSEP)conn$(OFILE): $(CRYPT_LIB)
 $(MTOBJODIR)$(DIRSEP)ssh$(OFILE): $(CRYPT_LIB)
 $(MTOBJODIR)$(DIRSEP)st_crypt$(OFILE): $(CRYPT_LIB)
-$(MTOBJODIR)$(DIRSEP)syncterm$(OFILE): $(CRYPT_LIB)
+$(MTOBJODIR)$(DIRSEP)syncterm$(OFILE): $(CRYPT_LIB) $(CIOLIB-MT)
 $(MTOBJODIR)$(DIRSEP)telnets$(OFILE): $(CRYPT_LIB)
 $(CIOLIB_INTERPOLATE_OBJS): $(CIOLIB-MT_BUILD)