bug#68690: Segmentation fault building with native-comp

[Stefan Monnier]

I've been spending a lot of time on this and still haven't found the
origin of the problem nor a fix.  Here's what I have currently, in
short:

    % src/bootstrap-emacs --batch -f batch-byte-compile lisp/ido.el 
    charset 0: a0000000f20e1328 => f1f2c070
    CHARSET_ATTRIBUTES(ID=0, cs=f1f2c064) = f20e132800000000 (@ f1f2c06c)
    
    lisp.h:1784: Emacs fatal error: assertion failed: VECTORLIKEP (a)

The first message comes from `dump_do_dump_relocation` when we load the
dump file and shows (I believe) the relocation we do for the
`attributes` field of the charset 0: we write the (relocated)
Lisp_Object value `a0000000f20e1328` at address `f1f2c070`.

The second message comes from `CHARSET_ATTRIBUTES` which tells us that
it reads the Lisp_Object value `f20e132800000000` at address `f1f2c06c`.

I sadly have no clue yet why there is this 4byte difference between
those two addresses (but it does explain the bogus Lisp_Object we get).


        Stefan