Log4cxx build fails on Mac OS X 10.4 while linking the library. The reason is the build system trying to link a C++ lib using gcc instead of g++. As I don't know much about ant and cpptask, I've not been able to change/fix this. But a workaround is to add
<syslibset libs="gcc_s.10.4" if="is-gcc"/>
to the build.xml file. Of course, the if-tag should be more specific to select Mac OS X 10.4 (and above?) only.
The correct fix would be to use g++ as linker for C++ libraries etc.