Build tweaks related to tags files.

* lib-src/Makefile.in (tagsfiles): New variable.
(TAGS): Also depend on the source files.  Use our own etags program.
* lisp/Makefile.in (ETAGS): Add EXEEXT.
(lisptagsfiles1, lisptagsfiles2, lisptagsfiles3, lisptagsfiles4):
Remove.
(tagsfiles): New, replacing lisptagsfiles1 etc.
Remove irrelevant source files here rather than in the TAGS rule.
(${ETAGS}): New rule.
(TAGS): Also depend on the etags executable.
* lwlib/Makefile.in (EXEEXT): New, set by configure.
(ETAGS): Add EXEEXT.
(${ETAGS}): New rule.
(ctagsfiles): Use "wildcard".
(TAGS): Also depend on the etags executable.
* nt/Makefile.in (ETAGS, tagsfiles): New variables.
(${ETAGS}): New rule.
(TAGS): Fix dependencies.
* oldXMenu/Makefile.in (EXEEXT): New, set by configure.
(ETAGS): New variable, replacing $TAGS.  Use our own etags program.
Remove "-t" argument.
(${ETAGS}): New rule.
(tagsfiles): New variable.
(TAGS): New rule, with proper dependencies.
* src/Makefile.in (ETAGS): Add EXEEXT.  Add a build rule.
(ctagsfiles1, ctagsfiles2): Use "wildcard".
(ctagsfiles3): Remove.
(TAGS): Depend on etags.
(../lisp/TAGS, $(lwlibdir)/TAGS): Let the rules in the relevant
directories decide if updates are needed.

oldXMenu/Makefile.in

@@ -58,12 +58,12 @@ CC=@CC@
 CFLAGS=@CFLAGS@
 CPPFLAGS = @CPPFLAGS@
 
-TAGS = etags
 RM = rm -f
 RANLIB = @RANLIB@
 AR = @AR@
 ARFLAGS = @ARFLAGS@
 MKDIR_P = @MKDIR_P@
+EXEEXT = @EXEEXT@
 
 OBJS =  Activate.o \
 	AddPane.o \
@@ -152,8 +152,17 @@ clean mostlyclean:
 bootstrap-clean maintainer-clean distclean: clean
 	rm -f Makefile
 
-.PHONY: tags
-tags:
-	$(TAGS) -t *.[ch]
+ETAGS = ../lib-src/etags${EXEEXT}
+
+${ETAGS}: FORCE
+	${MAKE} -C ../lib-src $(notdir $@)
+
+tagsfiles = $(wildcard ${srcdir}/*.[ch])
+
+FORCE:
+.PHONY: tags FORCE
+tags: TAGS
+TAGS: ${ETAGS} ${tagsfiles}
+	${ETAGS} ${tagsfiles}
 
 ### Makefile.in ends here