Inline some conversion methods around OsStr

[tesuji]

Diff on the assembly of this snippet before and after this PR: https://www.diffchecker.com/NeGMjaJ2

use std::env;
use std::io;
use std::path::{Path, PathBuf};

pub fn cargo_home_with_cwd(cwd: &Path) -> io::Result<PathBuf> {
    match env::var_os("CARGO_HOME").filter(|h| !h.is_empty()) {
        Some(home) => {
            let home = PathBuf::from(home);
            if home.is_absolute() {
                Ok(home)
            } else {
                Ok(cwd.join(&home))
            }
        }
        _ => env::home_dir()
            .map(|p| p.join(".cargo"))
            .ok_or_else(|| io::Error::new(io::ErrorKind::Other, "could not find cargo home dir")),
    }
}

[rust-highfive]

r? @joshtriplett

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[Centril]

r? @alexcrichton

[alexcrichton]

@bors: r+

[bors]

📌 Commit 5f3f1a3 has been approved by alexcrichton