Split RBCONFIG recipe

And make `ifchange` a pipeline; it works even on Windows now.

Author: nobu

common.mk

@@ -938,19 +938,23 @@ rbconfig.rb: $(RBCONFIG)
 
 $(HAVE_BASERUBY:no=)$(RBCONFIG)$(HAVE_BASERUBY:no=): $(PREP)
 $(RBCONFIG): $(tooldir)/mkconfig.rb config.status $(srcdir)/version.h $(srcdir)/common.mk
+$(RBCONFIG): unicode-version
+
+unicode-version:
 	$(Q)$(BOOTSTRAPRUBY) -n \
 	-e 'BEGIN{version=ARGV.shift;mis=ARGV.dup}' \
 	-e 'END{abort "UNICODE version mismatch: #{mis}" unless mis.empty?}' \
 	-e '(mis.delete(ARGF.path); ARGF.close) if /ONIG_UNICODE_VERSION_STRING +"#{Regexp.quote(version)}"/o' \
 	$(UNICODE_VERSION) $(UNICODE_DATA_HEADERS)
+
+$(RBCONFIG):
 	$(Q)$(BOOTSTRAPRUBY) $(tooldir)/mkconfig.rb \
 		-arch=$(arch) -version=$(RUBY_PROGRAM_VERSION) \
 		-install_name=$(RUBY_INSTALL_NAME) \
 		-so_name=$(RUBY_SO_NAME) \
 		-unicode_version=$(UNICODE_VERSION) \
 		-unicode_emoji_version=$(UNICODE_EMOJI_VERSION) \
-	> rbconfig.tmp
-	$(IFCHANGE) "--timestamp=$@" rbconfig.rb rbconfig.tmp
+	| $(IFCHANGE) "--timestamp=$@" rbconfig.rb -
 
 test-rubyspec: test-spec
 yes-test-rubyspec: yes-test-spec