Resolve thread_local_initializer_can_be_made_const clippy lint

    warning: initializer for `thread_local` value can be made `const`
      --> tests/test.rs:20:34
       |
    20 |     static CORRECT: Cell<bool> = Cell::new(false);
       |                                  ^^^^^^^^^^^^^^^^ help: replace with: `const { Cell::new(false) }`
       |
       = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#thread_local_initializer_can_be_made_const
       = note: `-W clippy::thread-local-initializer-can-be-made-const` implied by `-W clippy::all`
       = help: to override `-W clippy::all` add `#[allow(clippy::thread_local_initializer_can_be_made_const)]`

Author: dtolnay

tests/test.rs

@@ -17,7 +17,7 @@ use std::cell::Cell;
 use std::ffi::CStr;
 
 thread_local! {
-    static CORRECT: Cell<bool> = Cell::new(false);
+    static CORRECT: Cell<bool> = const { Cell::new(false) };
 }
 
 #[no_mangle]