The parent commit added a empty_entry_test shared library to the IncludeDirectories test. Some toolchains fail to create a shared library with no user-defined symbols, so provide a dummy symbol.
This is a regression introduced in commit 0d46e9a0 (Store includes from the same include_directories call together., 2013-01-20). Reported at http://thread.gmane.org/gmane.comp.programming.tools.cmake.user/46695/focus=7847
0d46e9a0