Miri fail to build on current master

[tiif]

On current master 2dbc4a2cf, ./miri build will emit

error[E0658]: `let` expressions in this position are unstable
   --> miri-script/src/commands.rs:678:20
    |
678 |         if !dep && let Some(target) = &target {
    |                    ^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: see issue #53667 <https://github.com/rust-lang/rust/issues/53667> for more information
    = help: add `#![feature(let_chains)]` to the crate attributes to enable
    = note: this compiler was built on 2025-03-05; consider upgrading it if it is out of date

error[E0658]: `let` expressions in this position are unstable
   --> miri-script/src/commands.rs:708:19
    |
708 |         if dep && let Some(target) = &target {
    |                   ^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: see issue #53667 <https://github.com/rust-lang/rust/issues/53667> for more information
    = help: add `#![feature(let_chains)]` to the crate attributes to enable
    = note: this compiler was built on 2025-03-05; consider upgrading it if it is out of date

For more information about this error, try `rustc --explain E0658`.
error: could not compile `miri-script` (bin "miri-script") due to 2 previous errors
Failed to build miri-script. Is the 'nightly' toolchain installed?

These changes are from #4324. On first glance, we probably need to update our compiler version?

[tiif]

This is weird, maybe there are some problems with my local config?

[oli-obk]

miri only ever builds with the rustc version defined in https://github.com/rust-lang/miri/blob/master/rust-version

you may need to set it up again https://github.com/rust-lang/miri/blob/master/CONTRIBUTING.md#preparing-the-build-environment

[oli-obk]

ah miri-script gets built with nightly, so you may have to install/update that via rustup

[tiif]

Yup rustup update works, thanks!