Add workaround for multirust directory in testing

The home directory is a dummy one during the tests but the .multirust
directory in the real home remains in $PATH. Instead of filtering
$HOME/.multirust, it is necessary to filter any $PATH entry containing
.multirust as a component.

src/rustup-cli/self_update.rs

@@ -37,7 +37,7 @@ use rustup_utils::utils;
 use sha2::{Sha256, Digest};
 use std::env;
 use std::env::consts::EXE_SUFFIX;
-use std::path::{Path, PathBuf};
+use std::path::{Path, PathBuf, Component};
 use std::process::{self, Command};
 use std::fs::{self, File};
 use std::io::Read;
@@ -298,9 +298,9 @@ fn rustc_or_cargo_exists_in_path() -> bool {
     if let Some(paths) = env::var_os("PATH") {
         // Ignore rustc and cargo if present in $HOME/.cargo/bin and $HOME/.multirust/,
         // those are expected
-        let multirust_meta_path = env::home_dir().map(|path| path.join(".multirust")).unwrap();
         let paths = env::split_paths(&paths)
-            .filter(|path| !path.ends_with(".cargo/bin") && !path.starts_with(&multirust_meta_path));
+            .filter(|path| !path.ends_with(".cargo/bin") &&
+                    !path.components().any(|c| c == Component::Normal(".multirust".as_ref())));
 
         for path in paths {
             let rustc = path.join("rustc");