ocamlc -custom breaks bytecode execution

In Ubuntu Oneiric:

Using ubuntu's ocamlc:

edmcman@joethecat:~/ocaml-3.12.0$ ocamlc -custom test.ml -o test.out
edmcman@joethecat:~/ocaml-3.12.0$ ocamlrun test.out
Fatal error: the file test.out is not a bytecode executable file

Using the official ocaml 3.12.0 source:

edmcman@joethecat:~/ocaml-3.12.0$ ocamlrun ./ocamlc -custom test.ml -o test.out
edmcman@joethecat:~/ocaml-3.12.0$ ocamlrun test.out

This bug is preventing users of our OCaml project from being able to debug their binaries, because ocamldebug reports the same error as ocamlrun.