The GPRclean tool removes the files created by GPRbuild.
At a minimum, to invoke GPRclean you must specify a main project file
in a command such as gprclean proj.gpr or gprclean -P proj.gpr.
Examples of invocation of GPRclean:
gprclean -r prj1.gpr
gprclean -c -P prj2.gpr