pseudo: Enhancements

Enable changing the data directory on the fly from the environment and then use
this feature within poky to confine pseudo usage to each WORKDIR.

This fixes issues that could be seen under heavy inode reusage e.g.
with rm_work.

Work based mainly off a patch from Joshua Lock but finished by Richard
Purdie.

Signed-off-by: Richard Purdie <rpurdie@linux.intel.com>

meta/classes/base.bbclass

@@ -148,6 +148,7 @@ python base_do_setscene () {
 		bb.build.make_stamp("do_setscene", d)
 }
 do_setscene[selfstamp] = "1"
+do_setscene[dirs] = "${PSEUDO_DATADIR}"
 addtask setscene before do_fetch
 
 addtask fetch