Replace ancient lazy_static crate with once_cell

Piggybacking on the [motivation in winit]: `lazy_static!` is a macro
whereas `once_cell` achieves the same using generics.  Its
implementation has also been [proposed for inclusion in `std`], making
it easier to switch to a standardized version if/when that happens.  The
author of that winit PR is making this change to many more crates,
slowly turning the scales in favour of `once_cell` in most dependency
trees.  Furthermore `lazy_static` hasn't published any updates for 3
years.

See also [the `once_cell` F.A.Q.].

[motivation in winit]: rust-windowing/winit#2313
[proposed for inclusion in `std`]: rust-lang/rust#74465
[the `once_cell` F.A.Q.]: https://docs.rs/once_cell/latest/once_cell/#faq

Cargo.toml

@@ -17,7 +17,7 @@ libc = "0.2.121"
 regex = { version = "1.5.5", optional = true }
 
 [target.'cfg(windows)'.dependencies]
-lazy_static = "1.4.0"
+once_cell = "1"
 
 [dev-dependencies]
 tempfile = "3.3.0"

src/finder.rs

@@ -151,29 +151,31 @@ impl Finder {
     where
         P: IntoIterator<Item = PathBuf>,
     {
+        use once_cell::sync::Lazy;
+
         // Sample %PATHEXT%: .COM;.EXE;.BAT;.CMD;.VBS;.VBE;.JS;.JSE;.WSF;.WSH;.MSC
         // PATH_EXTENSIONS is then [".COM", ".EXE", ".BAT", …].
         // (In one use of PATH_EXTENSIONS we skip the dot, but in the other we need it;
         // hence its retention.)
-        lazy_static! {
-            static ref PATH_EXTENSIONS: Vec<String> =
-                env::var("PATHEXT")
-                    .map(|pathext| {
-                        pathext.split(';')
-                            .filter_map(|s| {
-                                if s.as_bytes().first() == Some(&b'.') {
-                                    Some(s.to_owned())
-                                } else {
-                                    // Invalid segment; just ignore it.
-                                    None
-                                }
-                            })
-                            .collect()
-                    })
-                    // PATHEXT not being set or not being a proper Unicode string is exceedingly
-                    // improbable and would probably break Windows badly. Still, don't crash:
-                    .unwrap_or_default();
-        }
+        static PATH_EXTENSIONS: Lazy<Vec<String>> = Lazy::new(|| {
+            env::var("PATHEXT")
+                .map(|pathext| {
+                    pathext
+                        .split(';')
+                        .filter_map(|s| {
+                            if s.as_bytes().first() == Some(&b'.') {
+                                Some(s.to_owned())
+                            } else {
+                                // Invalid segment; just ignore it.
+                                None
+                            }
+                        })
+                        .collect()
+                })
+                // PATHEXT not being set or not being a proper Unicode string is exceedingly
+                // improbable and would probably break Windows badly. Still, don't crash:
+                .unwrap_or_default()
+        });
 
         paths
             .into_iter()

src/lib.rs

@@ -14,10 +14,6 @@
 //!
 //! ```
 
-#[cfg(windows)]
-#[macro_use]
-extern crate lazy_static;
-
 mod checker;
 mod error;
 mod finder;