Please extend the dirclean target

[brummer10]

I'm running into a very strange issue during working on a plugin. In the first build I've setup the modgui folder wrong, I corrected that, run ./build moddwarf plug-dirclean and rebuild. From that point on I always end up with a duplicated modgui contend in the root folder. It took me a long time to find out what goes wrong.
I found a copy of the first build under
/mod-workdir/moddwarf/target/usr/lib/lv2
and from there the builder copies over the old modgui contend to the fresh build in plugins.
After delete that one, I'm able to build my plug clean.
It would be very nice when you could add the deletion of the plugin copy under /mod-workdir/moddwarf/target/usr/lib/lv2 to the dirclean command to avoid such trouble.