stacktfrace fails as N_push has an ExtLink to Expr, but Expr is not yet supported in the serialisation of ExtLink

When compiling

module bug;

use Array: {sel, genarray};
export all;



inline
int[*] genarrayI (int[.] shp, int[*] a)
{
    return {iv -> genarray (shp, a[iv]) };
}

with sac2c-d -check s -noprelude bug.sac using sac2c 2.1.0-PuurGeluk-205-gbed27 I get:

**  8: Processing exports ...
Internal compiler error
Program reached impossible state at /Volumes/Users/sbs/sac2c/src/libsac2c/serialize/serialize_attribs.c:696 -- unknown target for ExtLink found!