Simplify the hierarchy target's logic. [0]

Run hierarchy with WORLDTMP in the path so it works when it is invoked
directly.  Such use is nearly alwasy wrong but appears to be common.[1]

PR:		conf/178209 [0], conf/178547 [1]
Submitted by:	Garrett Cooper <yaneurabeya@gmail.com> [0]
MFC after:	5 days
Fix typo (dbM -> dBm)

Submitted by:	Daan@vitsch.nl
Reviewed by:	adrian