make this build.rs link more similar to the others

Author: japaric

ci/main/rt/build.rs

@@ -1,19 +1,14 @@
-use std::env;
-use std::error::Error;
-use std::fs::File;
-use std::io::Write;
-use std::path::PathBuf;
+use std::{env, error::Error, fs::File, io::Write, path::PathBuf};
 
 fn main() -> Result<(), Box<Error>> {
     // build directory for this crate
-    let mut out = PathBuf::from(env::var_os("OUT_DIR").unwrap());
+    let out_dir = PathBuf::from(env::var_os("OUT_DIR").unwrap());
 
     // extend the library search path
-    println!("cargo:rustc-link-search={}", out.display());
+    println!("cargo:rustc-link-search={}", out_dir.display());
 
     // put `link.x` in the build directory
-    out.push("link.x");
-    File::create(out)?.write_all(include_bytes!("link.x"))?;
+    File::create(out_dir.join("link.x"))?.write_all(include_bytes!("link.x"))?;
 
     Ok(())
 }