Fix 1989/jar.2/Makefile for make everything/alt

The problem was that the alt rule had the ${CC} ... when it's not
supposed to. That's for the rule ${PROG}.alt which there is none in this
entry as there is no alt code.

1989/jar.2/Makefile

@@ -140,7 +140,7 @@ ${PROG}: ${PROG}.c
 # alternative executable
 #
 alt: data ${ALT_TARGET}
-	${CC} ${CFLAGS} $< -o $@ ${LDFLAGS}
+	@${TRUE}
 
 # data files
 #