Since Rafi pushed 223bbc8bd50a34282ef02952392fd4321113f770 my Linux
(Fedora 21) builds have been failing . I've finally tracked it down
to some problem with ccache-swig.
So if you have ccache installed (which is generally a good idea as it
speeds up builds a lot) you need to avoid the ccache version of swig. If
cmake is using the version of swig which doesn't work you will see that
the swig found is in /usr/lib64/ccache/swig
Do this either by using ccmake (or cmake-gui) to change SWIG_EXECUTABLE
to /usr/bin/swig or by using -DSWIG_EXECUTABLE=/usr/bin/swig on the
initial cmake line.
I don't know if this information is also true for Debian/Ubuntu with
 The errors look like this:
[2/4] Swig source
Syntax error in input(1).
ninja: build stopped: cannot make progress due to previous errors.