CMake should be able to relink automatically when a particular library changes if you follow the tips here: http://www.cmake.org/pipermail/cmake/2010-November/041072.html
The main idea is to give a full path to target_link_libraries(), rather than just the library name. If you give a full path, CMake will actually inspect the file for modification and relink if it has changed.
If you prefer to explicitly trigger relinking yourself, you can use add_custom_command to make a command like make link
which will remove the executable and then trigger a regular make
to rebuild it.