Rebuild with cargo creusot prove

[Lysxia]

Fixes #1279

[jhjourdan]

LGTM, thanks !

[jhjourdan]

Tehre is a new warning that seems to be related with this PR:

warning: unused `std::result::Result` that must be used
  --> cargo-creusot/src/main.rs:48:13
   |
48 |             creusot(None, cargs.options, cargs.cargo_flags);
   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: this `Result` may be an `Err` variant, which should be handled
   = note: `#[warn(unused_must_use)]` on by default
help: use `let _ = ...` to ignore the resulting value
   |
48 |             let _ = creusot(None, cargs.options, cargs.cargo_flags);
   |             +++++++