Use Build::getenv instead of env::var* in anywhere that makes sense

clippy.toml

@@ -0,0 +1,4 @@
+disallowed-methods = [
+    { path = "std::env::var_os", reason = "Please use Build::getenv" },
+    { path = "std::env::var", reason = "Please use Build::getenv" },
+]

dev-tools/cc-test/build.rs

@@ -1,3 +1,5 @@
+#![allow(clippy::disallowed_methods)]
+
 use std::env;
 use std::fs;
 use std::path::{Path, PathBuf};

src/bin/gcc-shim.rs

@@ -2,6 +2,7 @@
 //! It is not intended for users and is not published with the library code to crates.io.
 
 #![cfg_attr(test, allow(dead_code))]
+#![allow(clippy::disallowed_methods)]
 
 use std::env;
 use std::fs::File;

src/command_helpers.rs

@@ -27,6 +27,7 @@ pub(crate) struct CargoOutput {
 
 impl CargoOutput {
     pub(crate) fn new() -> Self {
+        #[allow(clippy::disallowed_methods)]
         Self {
             metadata: true,
             warnings: true,

src/tool.rs

@@ -6,7 +6,7 @@ use std::{
     io::Write,
     path::{Path, PathBuf},
     process::{Command, Stdio},
-    sync::Mutex,
+    sync::RwLock,
 };
 
 use crate::{
@@ -40,7 +40,7 @@ pub struct Tool {
 impl Tool {
     pub(crate) fn new(
         path: PathBuf,
-        cached_compiler_family: &Mutex<HashMap<Box<Path>, ToolFamily>>,
+        cached_compiler_family: &RwLock<HashMap<Box<Path>, ToolFamily>>,
         cargo_output: &CargoOutput,
         out_dir: Option<&Path>,
     ) -> Self {
@@ -57,7 +57,7 @@ impl Tool {
     pub(crate) fn with_clang_driver(
         path: PathBuf,
         clang_driver: Option<&str>,
-        cached_compiler_family: &Mutex<HashMap<Box<Path>, ToolFamily>>,
+        cached_compiler_family: &RwLock<HashMap<Box<Path>, ToolFamily>>,
         cargo_output: &CargoOutput,
         out_dir: Option<&Path>,
     ) -> Self {
@@ -90,7 +90,7 @@ impl Tool {
         path: PathBuf,
         clang_driver: Option<&str>,
         cuda: bool,
-        cached_compiler_family: &Mutex<HashMap<Box<Path>, ToolFamily>>,
+        cached_compiler_family: &RwLock<HashMap<Box<Path>, ToolFamily>>,
         cargo_output: &CargoOutput,
         out_dir: Option<&Path>,
     ) -> Self {
@@ -186,13 +186,13 @@ impl Tool {
             }
         }
         let detect_family = |path: &Path| -> Result<ToolFamily, Error> {
-            if let Some(family) = cached_compiler_family.lock().unwrap().get(path) {
+            if let Some(family) = cached_compiler_family.read().unwrap().get(path) {
                 return Ok(*family);
             }
 
             let family = detect_family_inner(path, cargo_output, out_dir)?;
             cached_compiler_family
-                .lock()
+                .write()
                 .unwrap()
                 .insert(path.into(), family);
             Ok(family)

src/utilities.rs

@@ -15,7 +15,7 @@ where
 {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         let len = self.slice.len();
-        for (index, os_str) in self.slice.into_iter().enumerate() {
+        for (index, os_str) in self.slice.iter().enumerate() {
             // TODO: Use OsStr::display once it is stablised,
             // Path and OsStr has the same `Display` impl
             write!(f, "{}", Path::new(os_str).display())?;