Revert r65800

"Makefile.in: reconfig with the original warnflags"
It would be unnecessary since r65803 and r65805.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@66835 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

Makefile.in

@@ -358,7 +358,6 @@ reconfig-exec-1 = set -x; "$$@"
 reconfig config.status:	$(srcdir)/$(CONFIGURE) $(srcdir)/enc/Makefile.in \
 			$(srcdir)/include/ruby/version.h
 	@PWD= MINIRUBY="$(MINIRUBY)"; export MINIRUBY; \
-	warnflags="@warnflags@"; export warnflags; \
 	set $(SHELL) $($@-args); $(reconfig-exec-$(V))
 
 $(srcdir)/$(CONFIGURE): $(srcdir)/configure.ac $(srcdir)/aclocal.m4