https://issues.dlang.org/show_bug.cgi?id=13603

          Issue ID: 13603
           Summary: rdmd: if dmd.conf is missing, always rebuilds the
                    target
           Product: D
           Version: D2
          Hardware: x86
                OS: Mac OS X
            Status: NEW
          Severity: normal
          Priority: P1
         Component: tools
          Assignee: nobody@puremagic.com
          Reporter: andrei@erdani.com

When starting dmd is looking for its config file, e.g. /etc/dmd.conf. If that's missing, all works fine as far as dmd is concerned. However, rdmd considers the missing config file infinitely newer than the target and therefore always builds the target.

--