Always one of those dreaded moments after updating Ubuntu, to 13.04 this time. Will QGIS compile properly. Not as it turned out, but the solutions were easy and quick, thanks to posts on nyalldawson.net and boringnerdystuff.
Ubuntu 13.04 defaults to Qt 5. You could solve this by changing back to Qt4, but as one pointed out in the comments on Nyall Dawson’s post, making system-wide changes to compile a single piece of software might be a bit of an overkill. Instead, what worked for me was to change in the configure options:
from: -DQMAKE_EXECUTABLE=/usr/bin/qmake to: -DQMAKE_EXECUTABLE=/usr/bin/qmake-qt4
You may also need to set -DQT_INCLUDE_DIR=/usr/include/qt4 as suggested in the above-mentioned comment. In my case it was already set, so I didn’t need to change it.
The next error was that libpython2.7.so was not found in /usr/lib. Following Nyal Dawson’s suggestion, I found it in /usr/lib/x86_64-linux-gnu/.
Creating a softlink did the trick: ln -sf /usr/lib/x86_64-linux-gnu/libpython2.7.so /usr/lib/libpython2.7.so sudo ldconfig
Update from Nyal Dawson: change the PYTHON_LIBRARY option:
from: /usr/lib/libpython2.7.so to: /usr/lib/x86_64-linux-gnu/libpython2.7.so
And now QGIS is up and running again, thanks to the above-mentioned two posts.