rust-lang/rust-clippy#15842

    warning: this could be rewritten as `let...else`
      --> build.rs:80:5
       |
    80 | /     let rustc = match rustc {
    81 | |         Some(rustc) => rustc,
    82 | |         None => return,
    83 | |     };
       | |______^ help: consider writing: `let Some(rustc) = rustc else { return };`
       |
       = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#manual_let_else
       = note: `-W clippy::manual-let-else` implied by `-W clippy::pedantic`
       = help: to override `-W clippy::pedantic` add `#[allow(clippy::manual_let_else)]`

    warning: lint `clippy::empty_enum` has been renamed to `clippy::empty_enums`
       --> tests/test_display.rs:183:13
        |
    183 |     #[allow(clippy::empty_enum)]
        |             ^^^^^^^^^^^^^^^^^^ help: use the new name: `clippy::empty_enums`
        |
        = note: `#[warn(renamed_and_removed_lints)]` on by default

    error[E0453]: allow(clippy::needless_lifetimes) incompatible with previous forbid
      --> tests/test_lints.rs:52:14
       |
    50 |     #![forbid(clippy::needless_lifetimes)]
       |               -------------------------- `forbid` level set here
    51 |
    52 |     #[derive(Error, Debug)]
       |              ^^^^^ overruled by previous forbid
       |
       = note: this error originates in the derive macro `Error` (in Nightly builds, run with -Z macro-backtrace for more info)

Made clippy lifetime allows conditional