Index: ruby-1.9.3-p392/lib/mkmf.rb
===================================================================
--- ruby-1.9.3-p392.orig/lib/mkmf.rb
+++ ruby-1.9.3-p392/lib/mkmf.rb
@@ -2039,8 +2039,8 @@ static: $(STATIC_LIB)#{$extout ? " insta
       end
       for f in files
         dest = "#{dir}/#{File.basename(f)}"
-        mfile.print("install-rb#{sfx}: #{dest} #{dir}\n")
-        mfile.print("#{dest}: #{f}\n")
+        mfile.print("install-rb#{sfx}: #{dest}\n")
+        mfile.print("#{dest}: #{f} #{timestamp_file(dir)}\n")
         mfile.print("\t$(Q) $(#{$extout ? 'COPY' : 'INSTALL_DATA'}) #{f} $(@D#{sep})\n")
         if defined?($installed_list) and !$extout
           mfile.print("\t@echo #{dest}>>$(INSTALLED_LIST)\n")