In GG, "make install" gives the following error :
-- Up-to-date: /usr/local/lib/pkgconfig/GiGiOgre.pc
CMake Error at cmake_install.cmake:52 (FILE):
file INSTALL cannot find
"/home/flver/cvs_svn/freeorion/trunk/FreeOrion/GG/doc/GG".
make: *** [install] Erreur 1
The doc directory contains :
Doxyfile GGDoc.txt
So, I suppose the doc is not generated automatically.
There should be an option BUILD_DOCUMENTATION in ccmake to set whether to build and install the GG documentation. It should also not attempt to build or install the documentation if Doxygen is not found. I don't know why it's apparently trying to install after not building it for you, but try fiddling with the options in ccmake.
Should be fixed in SVN.