fix up r58573

* common.mk: make the directory for extension shared library with
  the timestamp directory.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@58583 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

common.mk

@@ -773,7 +773,7 @@ $(ENC_TRANS_D):
 	@exit > $@
 
 $(TIMESTAMPDIR)/$(arch)/.time:
-	$(Q)$(MAKEDIRS) $(@D)
+	$(Q)$(MAKEDIRS) $(@D) $(EXTOUT)/$(arch)
 	@exit > $@
 
 ###