patch by Younes Khoudli (changed slightly). Thanks
@ -22,7 +22,7 @@ config.h:
$(CC) $(STCFLAGS) -c $<
st.o: config.h st.h win.h
x.o: arg.h st.h win.h
x.o: arg.h config.h st.h win.h
$(OBJ): config.h config.mk