I am not sure if gcc was able to compile itself always, but if it was, you can argue that there existed a smallest kernel of gcc sometime ago that did not depend on any of the "features" of gcc that makes it impossible for other compilers to compile gcc. Now, if there existed such a thing before, it probably exists now, because the incremental "features" that make it impossible for other compilers to compile gcc, would make it impossible for gcc too. My bet would be that there exists a logical separation somewhere, and there is still a small kernel in it, that you can bootstrap with other compilers, from which point you can do what your parent says.