Makefile.in: use ASMEXT in implicit rules

Use $(ASMEXT) instead of `.s` directly, as well as `.SUFFIXES:`
line.

Also, use the same suffix at compiling from `.c`.  These are
different things traditionally, but we won't mix same name files
with `.c` and `.s`.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@65951 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

Makefile.in

@@ -407,11 +407,11 @@ $(srcdir)/enc/jis/props.h: enc/jis/props.kwd
 	@$(ECHO) compiling $<
 	$(Q) $(CC) $(CFLAGS) $(XCFLAGS) $(CPPFLAGS) $(COUTFLAG)$@ -c $<
 
-.s.@OBJEXT@:
+.$(ASMEXT).@OBJEXT@:
 	@$(ECHO) assembling $<
 	$(Q) $(CC) $(ASFLAGS) -o $@ -c $<
 
-.c.S:
+.c.$(ASMEXT):
 	@$(ECHO) translating $<
 	$(Q) $(CC) $(CFLAGS) $(XCFLAGS) $(CPPFLAGS) $(COUTFLAG)$@ -S $<