examples: rely on ylwrap

Reported by Thomas Petazzoni.
https://lists.gnu.org/archive/html/bug-bison/2019-08/msg00000.html

* examples/c/reccalc/scan.l: Generate scan.h.
* examples/c/reccalc/local.mk: Remove dedicated rules, leave the
handling of multiple outputs to Automake's ylwrap.

THANKS

@@ -171,6 +171,7 @@ Sum Wu                    sum@geekhouse.org
 Théophile Ranquet         theophile.ranquet@gmail.com
 Thiru Ramakrishnan        thiru.ramakrishnan@gmail.com
 Thomas Jahns              jahns@dkrz.de
+Thomas Petazzoni          thomas.petazzoni@bootlin.com
 Tim Josling               tej@melbpc.org.au
 Tim Landscheidt           tim@tim-landscheidt.de
 Tim Van Holder            tim.van.holder@pandora.be

examples/c/reccalc/local.mk

@@ -37,18 +37,6 @@ endif FLEX_WORKS
 DASH = -
 %D%/reccalc$(DASH)parse.o: %D%/scan.h
 
-%D%/scan.c %D%/scan.h: %D%/scan.stamp
-	@test -f $@ || rm -f %D%/scan.stamp
-	@test -f $@ || $(MAKE) $(AM_MAKEFLAGS) %D%/scan.stamp
-
-%D%/scan.stamp: %D%/scan.l
-	$(AM_V_LEX)rm -f $@ $@.tmp
-	$(AM_V_at)$(MKDIR_P) %D%
-	$(AM_V_at)touch $@.tmp
-	$(AM_V_at)$(LEX) -o%D%/scan.c --header-file=%D%/scan.h $(srcdir)/%D%/scan.l
-	$(AM_V_at)mv $@.tmp $@
-
-
 EXTRA_DIST += %D%/reccalc.test %D%/scan.l
 dist_reccalc_DATA = %D%/parse.y %D%/scan.l %D%/Makefile %D%/README.md
 CLEANFILES += %D%/parse.[ch] %D%/parse.output %D%/scan.[ch] %D%/*.stamp

examples/c/reccalc/scan.l

@@ -3,7 +3,7 @@
 /* Disable Flex features we don't need, to avoid warnings. */
 %option nodefault noinput nounput noyywrap
 
-%option reentrant
+%option reentrant header-file="scan.h"
 
 %{
 #include <assert.h>