m: Remove once_cell dependency

Removes the once_cell dependency, instead using std::sync::OnceLock and a
minimal polyfill for std::sync::LazyLock, which may be stabilized soon
(see rust-lang/rust#121377).

This should not require a bump in MSRV, as OnceLock was stabilized in 1.70,
which this crate is using.

src/platform_impl/linux/common/xkb/mod.rs

@@ -3,8 +3,8 @@ use std::os::raw::c_char;
 use std::ptr::{self, NonNull};
 use std::sync::atomic::{AtomicBool, Ordering};
 
+use crate::utils::Lazy;
 use log::warn;
-use once_cell::sync::Lazy;
 use smol_str::SmolStr;
 #[cfg(wayland_platform)]
 use std::os::unix::io::OwnedFd;

src/platform_impl/linux/mod.rs

@@ -11,7 +11,7 @@ use std::{collections::VecDeque, env, fmt};
 use std::{ffi::CStr, mem::MaybeUninit, os::raw::*, sync::Mutex};
 
 #[cfg(x11_platform)]
-use once_cell::sync::Lazy;
+use crate::utils::Lazy;
 use smol_str::SmolStr;
 
 #[cfg(x11_platform)]

src/platform_impl/linux/x11/ime/input_method.rs

@@ -8,7 +8,7 @@ use std::{
 };
 
 use super::{super::atoms::*, ffi, util, XConnection, XError};
-use once_cell::sync::Lazy;
+use crate::utils::Lazy;
 use x11rb::protocol::xproto;
 
 static GLOBAL_LOCK: Lazy<Mutex<()>> = Lazy::new(Default::default);

src/platform_impl/linux/x11/util/wm.rs

@@ -1,6 +1,6 @@
 use std::sync::Mutex;
 
-use once_cell::sync::Lazy;
+use crate::utils::Lazy;
 
 use super::*;