Arrgh. A clean pc98 build failed due to bogons on my part :-(.

Fix it by putting back the link of machine to sys/i386/include rather
than ../../include (aka sys/pc98/include).  I had a stale machine link
on my first test.

Not sure what the "right" fix is, but this unbreaks things.

sys/conf/Makefile.pc98

@@ -30,6 +30,7 @@ S=	../../..
 .endif
 .include "$S/conf/kern.pre.mk"
 
+EXTRA_GENASSYM=rm -f ./machine ; ln -s $S/$M/include ./machine
 MKMODULESENV+=	MACHINE=pc98
 
 %BEFORE_DEPEND

sys/conf/kern.post.mk

@@ -74,6 +74,9 @@ assym.s: $S/kern/genassym.sh genassym.o
 	NM=${NM} OBJFORMAT=elf sh $S/kern/genassym.sh genassym.o > ${.TARGET}
 
 genassym.o: $S/$M/$M/genassym.c
+.if defined(EXTRA_GENASSYM)
+	${EXTRA_GENASSYM}
+.endif
 	${CC} -c ${CFLAGS} $S/$M/$M/genassym.c
 
 ${SYSTEM_OBJS} genassym.o vers.o: opt_global.h