bitcoin/bitcoin — pull request #1415 by dooglus (2012-06-03 23:15:07+00:00)
Title: "USE_UPNP=-" is needed to remove UPnP support.

The text file is wrong on how to build without UPNP support, as shown below:

$qmake USE_UPNP=
Project MESSAGE: Building with UPNP support

$ qmake USE_UPNP=-
Project MESSAGE: Building without UPNP support