WITH_META_MODE: Fix rebuilding maketab outside of build-tools.

The bsd.dep.mk yacc targets rely on only the .c file getting a .meta
file.  However the previous code here relying on only the .h file meant
that it would be generated with a .meta file.  r301285 made it so that
the .h file is never expected to get a .meta file.  To keep this
restriction in place add in an extra dependency on the .c file so that
it is generated at this time.  It's a hack but the best for the patterns
we have at the moment for handling build-tools and side-effect-generated
files.

Reported by:	Mark Millard
Approved by:	re (implicit)
Sponsored by:	EMC / Isilon Storage Division

usr.bin/awk/Makefile

@@ -17,8 +17,10 @@ MLINKS=	awk.1 nawk.1
 
 CLEANFILES= maketab proctab.c ytab.h
 
-ytab.h: awkgram.h .NOMETA
-	ln -sf ${.ALLSRC} ${.TARGET}
+# XXX: awkgram.c isn't really needed here but it is added to keep
+# awkgram.h: .NOMETA respected.
+ytab.h: awkgram.c awkgram.h .NOMETA
+	ln -sf ${.ALLSRC:M*.h} ${.TARGET}
 
 proctab.c: maketab
 	${BTOOLSPATH:U.}/maketab > proctab.c