Rollup merge of #22727 - alexcrichton:prep-env, r=aturon

 This commit moves `std::env` away from the `std::old_io` error type as well as
the `std::old_path` module. Methods returning an error now return `io::Error`
and methods consuming or returning paths use `std::path` instead of
`std::old_path`. This commit does not yet mark these APIs as `#[stable]`.

This commit also migrates `std::old_io::TempDir` to `std::fs::TempDir` with
essentially the exact same API. This type was added to interoperate with the new
path API and has its own `tempdir` feature.

Finally, this commit reverts the deprecation of `std::os` APIs returning the old
path API types. This deprecation can come back once the entire `std::old_path`
module is deprecated.

[breaking-change]

1 files changed, 2 insertions, 1 deletions

diff --git a/src/librustc_back/target/mod.rs b/src/librustc_back/target/mod.rs
index b04c07977c3..d09a7c355d3 100644
--- a/src/librustc_back/target/mod.rs
+++ b/src/librustc_back/target/mod.rs
@@ -310,6 +310,7 @@ impl Target {
     /// JSON decoding.
     pub fn search(target: &str) -> Result<Target, String> {
         use std::env;
+        use std::os;
         use std::ffi::OsString;
         use std::old_io::File;
         use std::old_path::Path;
@@ -396,7 +397,7 @@ impl Target {
 
         // FIXME 16351: add a sane default search path?
 
-        for dir in env::split_paths(&target_path) {
+        for dir in os::split_paths(target_path.to_str().unwrap()).iter() {
             let p =  dir.join(path.clone());
             if p.is_file() {
                 return load_file(&p);