b2/Makefile: generate dependencies also for YACC- and LEX-generated files

We need explicit rules to compile lex.yy.c and y.tab.c for the relaxed
CFLAGS. However, this means that the implicit rule was not used and
therefore no dependencies were generated.

b2/Makefile

@@ -46,6 +46,12 @@ else
 	DEPEND	= $(DEPEND_quiet)
 endif
 
+MKDEP = $(DEPEND) $(1).c | \
+	sed -e \
+	'/^\(.*:\)\? */{p;s///;s/ *\\\?$$/ /;s/  */:\n/g;H;}' \
+	  -e '$${g;p;}' -e d >$(1).d; \
+	[ "$${PIPESTATUS[*]}" = "0 0" ] || { rm -f $(1).d; exit 1; }
+
 .PHONY:	all clean spotless try
 
 all:		boom
@@ -58,20 +64,18 @@ lex.yy.c:	lang.l y.tab.h
 
 lex.yy.o:	lex.yy.c y.tab.h
 		$(CC) -c $(CFLAGS) $(SLOPPY) lex.yy.c
+		$(call MKDEP, lex.yy)
 
 y.tab.c y.tab.h: lang.y
 		$(YACC) $(YYFLAGS) -d lang.y
 
 y.tab.o:	y.tab.c
 		$(CC) -c $(CFLAGS) $(SLOPPY) y.tab.c
+		$(call MKDEP, y.tab)
 
 %.o:		%.c
 		$(CC) -c $(CFLAGS) $*.c -o $*.o
-		$(DEPEND) $*.c | \
-		  sed -e \
-		    '/^\(.*:\)\? */{p;s///;s/ *\\\?$$/ /;s/  */:\n/g;H;}' \
-		    -e '$${g;p;}' -e d >$*.d; \
-		  [ "$${PIPESTATUS[*]}" = "0 0" ] || { rm -f $*.d; exit 1; }
+		$(call MKDEP, $*)
 
 -include $(OBJS:.o=.d)