qtalchemy fails if pyside=rcc install to different prefix than python stuff

[Treeve Jelbert]

pyside and pyside-tools allow building by specifying SITE_PACKAGE which is
different to CMAKE_INSTALL_PREFIX.

I have both qt4 and qt5 installed.

In my case I used

CMAKE_INSTALL_PREFIX=/opt/qt4/
SITE_PACKAGE=/usr/lib/python2.7/site-packages


In this situation building qtalchemy fails, because it assumes that pyside-rcc
is in the same prefix as PySide

###
running build
running build_ui
compiling qtalchemy/widgets/icons.qrc -> qtalchemy/widgets/icons_rc.py
error: Unable to compile resource file [Errno 2] No such file or directory




$ which pyside-rcc
/opt/qt4/bin/pyside-rcc

$ which pyside-uic
/opt/qt4/bin/pyside-uic