Keep environment variables in a BTreeMap to preserve sort order

This prevents verbose output from varying between runs due to HashMap
(non-)ordering.

src/cargo/util/process_builder.rs

@@ -2,7 +2,7 @@ use crate::util::{process_error, read2, CargoResult, CargoResultExt};
 use anyhow::bail;
 use jobserver::Client;
 use shell_escape::escape;
-use std::collections::HashMap;
+use std::collections::BTreeMap;
 use std::env;
 use std::ffi::{OsStr, OsString};
 use std::fmt;
@@ -17,7 +17,7 @@ pub struct ProcessBuilder {
  /// A list of arguments to pass to the program.
  args: Vec<OsString>,
  /// Any environment variables that should be set for the program.
- env: HashMap<String, Option<OsString>>,
+ env: BTreeMap<String, Option<OsString>>,
  /// The directory to run the program from.
  cwd: Option<OsString>,
  /// The `make` jobserver. See the [jobserver crate][jobserver_docs] for
@@ -128,7 +128,7 @@ impl ProcessBuilder {
 
  /// Gets all environment variables explicitly set or unset for the process (not inherited
  /// vars).
- pub fn get_envs(&self) -> &HashMap<String, Option<OsString>> {
+ pub fn get_envs(&self) -> &BTreeMap<String, Option<OsString>> {
  &self.env
  }
 
@@ -334,7 +334,7 @@ pub fn process<T: AsRef<OsStr>>(cmd: T) -> ProcessBuilder {
  program: cmd.as_ref().to_os_string(),
  args: Vec::new(),
  cwd: None,
- env: HashMap::new(),
+ env: BTreeMap::new(),
  jobserver: None,
  display_env_vars: false,
  }