elf32: link to libc.so and libdl.so

No actual symbol resolution is done yet, not even dlsym. So hello.c
still does not work. Executing from linux is still broken somehow
(segfault). But starting using ld-linux.so.2 seems to work, e.g.

  /lib/ld-linux.so.2 ./test

Some notes: the glibc linker starts with _dl_start in elf/rtld.c, the
main function is dl_main.