Object files in arch_flags* must be regenerated

[reuk]

A recent change in CBMC made it an invariant of pointer_typet that pointers have a width field. On my development branch, I've added assert(!type.get(ID_width).empty()); to to_pointer_type so that I find all malformedpointer_typets.

This is fine, and I've found several places where pointer_typets are constructed incorrectly. The problem is that when the cross-compiled object files in the arch_flags regression tests are loaded, they contain malformed pointers, which cause the new assertions to fail.

The instructions in the test.desc files are not especially clear: it's not obvious how to set up an ARM cross-compiler.

More detailed instructions should be added to the test.desc files, and new object files should be submitted, generated with a more recent version of goto-cc.

Pinging @karkhaz and @tautschnig as they may be familiar with this process.

[karkhaz]

Please let me know if the instructions for generating cross-compiled binaries are still unclear.

[reuk]

LGTM