Avoid using env::temp when linking a binary

This keeps all build artefacts (even temporary ones) within the build directory.

Author: ChrisDenton

compiler/rustc_codegen_ssa/src/back/link.rs

@@ -103,17 +103,18 @@ pub fn link_binary(
         });
 
         if outputs.outputs.should_link() {
-            let tmpdir = TempDirBuilder::new()
-                .prefix("rustc")
-                .tempdir()
-                .unwrap_or_else(|error| sess.dcx().emit_fatal(errors::CreateTempDir { error }));
-            let path = MaybeTempDir::new(tmpdir, sess.opts.cg.save_temps);
             let output = out_filename(
                 sess,
                 crate_type,
                 outputs,
                 codegen_results.crate_info.local_crate_name,
             );
+            let tmpdir = TempDirBuilder::new()
+                .prefix("rustc")
+                .tempdir_in(output.parent().unwrap_or_else(|| Path::new(".")))
+                .unwrap_or_else(|error| sess.dcx().emit_fatal(errors::CreateTempDir { error }));
+            let path = MaybeTempDir::new(tmpdir, sess.opts.cg.save_temps);
+
             let crate_name = format!("{}", codegen_results.crate_info.local_crate_name);
             let out_filename = output.file_for_writing(
                 outputs,

compiler/rustc_fs_util/src/lib.rs

@@ -1,6 +1,6 @@
 use std::ffi::{CString, OsStr};
 use std::path::{Path, PathBuf, absolute};
-use std::{env, fs, io};
+use std::{fs, io};
 
 use tempfile::TempDir;
 
@@ -139,8 +139,4 @@ impl<'a, 'b> TempDirBuilder<'a, 'b> {
         }
         self.builder.tempdir_in(dir)
     }
-
-    pub fn tempdir(&self) -> io::Result<TempDir> {
-        self.tempdir_in(env::temp_dir())
-    }
 }