added functions to generator for setting compile flags and for unconditionally making targets
Can be used directly in a scipt by calling for example dune.generator.setFlags("-g") or dune.generator.unsetFlags() to get the flag used during configure and dune.generator.setNoDependencyCheck() and dune.generator.setDependencyCheck() before/after a module is compile, e.g., calling dune.grid.yaspGrid(...)