stubs for the executable from crtbegin.o into libc, which lets them be
excluded from static links that don't use them.
For this, drop the normal crt{begin,end}S.o from libc.so: the .init and .fini
sections for libc aren't called at the right times anyway, so it's good that
they're unused.  libc.so just needs __guard_local and the .note.openbsd.ident
section, so add them to stack_protector.c for now (this will be improved)
"good time" deraadt@