It's annoying that after touching a cxx file from Library_sw, it's not
enough to wait till it relinks, it also relinks CppunitTest_sw_uwriter
as well. So turn that one into a slowcheck, this way 'make sw' doesn't
relink it.

Change-Id: I0a8d956f57e92a9c6f1f91b727f492ca4c92c599