On Linux and a few other hosts, DMD uses gcc (or whatever is defined in the CC environment variable) to do its linking. Currently there seems to be no way to pass flags into this C compiler.
This becomes a problem when you NEED to change the flags passed into that compiler. The -Llinkerflag, unfortunately, doesn't help here. An example of this is issue 5278 (http://d.puremagic.com/issues/show_bug.cgi?id=5278). Without this patch, I would need to go through a lot of hoops just to upgrade my compiler every time.