$$PWD no longer works with qmake.cache.in

With Qt 5 beta 1, I was able to successfully use the qmake.cache.in feature to define custom path variables that would be visible in all the project files in a subdirs project I have been working on. One of these variables defined in qmake.cache.in was set to $$PWD. With Qt 5 beta 2, this longer works, and the variable does not resolve to the current path. I have been able to work around this issue by using $$PRO_FILE_PWD instead of $$PWD, but I imagine $$PWD is much more commonly used.