The project was not built due to "Internal error - the selected file is a system file that cannot be modified. It will be hidden.". Fix the problem, then try refreshing this project and building it since it may be inconsistent
This a problem encountered when the Clear Case plugin is added to the eclipse and then the project is imported.
By deleting the ".copyarea.db" in the bin directory of the concerned project would make it work. What is happening here is, when the project is trying to build, this particular file ".copyarea.db" (which is a read only file) stops it from executing. Once deleted physically going to the particular directory and then refreshing the project it would work.
Solution given by firstname.lastname@example.org