Copy built tools to stage sysroot

Motivation for this is to enable tools usage when using `rustup toolchain link`.

src/bootstrap/builder.rs

@@ -613,6 +613,27 @@ impl<'a> Builder<'a> {
         self.ensure(compile::Sysroot { compiler })
     }
 
+    pub fn sysroot_bindir(&self, compiler: Compiler) -> Interned<PathBuf> {
+        #[derive(Debug, Copy, Clone, Hash, PartialEq, Eq)]
+        struct Bindir {
+            compiler: Compiler,
+        }
+        impl Step for Bindir {
+            type Output = Interned<PathBuf>;
+
+            fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
+                run.never()
+            }
+
+            fn run(self, builder: &Builder<'_>) -> Interned<PathBuf> {
+                let sysroot_bindir = builder.sysroot(self.compiler).join("bin");
+                t!(fs::create_dir_all(&sysroot_bindir));
+                INTERNER.intern_path(sysroot_bindir)
+            }
+        }
+        self.ensure(Bindir { compiler })
+    }
+
     /// Returns the libdir where the standard library and other artifacts are
     /// found for a compiler's sysroot.
     pub fn sysroot_libdir(&self, compiler: Compiler, target: TargetSelection) -> Interned<PathBuf> {

src/bootstrap/compile.rs

@@ -1125,8 +1125,7 @@ impl Step for Assemble {
         // Link the compiler binary itself into place
         let out_dir = builder.cargo_out(build_compiler, Mode::Rustc, host);
         let rustc = out_dir.join(exe("rustc-main", host));
-        let bindir = sysroot.join("bin");
-        t!(fs::create_dir_all(&bindir));
+        let _ = builder.sysroot_bindir(target_compiler);
         let compiler = builder.rustc(target_compiler);
         builder.copy(&rustc, &compiler);
 

src/bootstrap/tool.rs

@@ -4,8 +4,6 @@ use std::fs;
 use std::path::PathBuf;
 use std::process::{exit, Command};
 
-use build_helper::t;
-
 use crate::builder::{Builder, Cargo as CargoCommand, RunConfig, ShouldRun, Step};
 use crate::channel::GitInfo;
 use crate::compile;
@@ -214,10 +212,17 @@ impl Step for ToolBuild {
             if tool == "tidy" {
                 tool = "rust-tidy";
             }
-            let cargo_out =
-                builder.cargo_out(compiler, self.mode, target).join(exe(tool, compiler.host));
-            let bin = builder.tools_dir(compiler).join(exe(tool, compiler.host));
+            let exe = exe(tool, compiler.host);
+            let cargo_out = builder.cargo_out(compiler, self.mode, target).join(&exe);
+            let bin = builder.tools_dir(compiler).join(&exe);
             builder.copy(&cargo_out, &bin);
+
+            // Don't create a stage0-sysroot/bin directory.
+            if compiler.stage > 0 {
+                let sysroot_bin = builder.sysroot_bindir(compiler).join(&exe);
+                builder.copy(&cargo_out, &sysroot_bin);
+            }
+
             Some(bin)
         }
     }
@@ -565,11 +570,9 @@ impl Step for Rustdoc {
             .cargo_out(build_compiler, Mode::ToolRustc, target)
             .join(exe("rustdoc_tool_binary", target_compiler.host));
 
-        // don't create a stage0-sysroot/bin directory.
+        // Don't create a stage0-sysroot/bin directory.
         if target_compiler.stage > 0 {
-            let sysroot = builder.sysroot(target_compiler);
-            let bindir = sysroot.join("bin");
-            t!(fs::create_dir_all(&bindir));
+            let bindir = builder.sysroot_bindir(target_compiler);
             let bin_rustdoc = bindir.join(exe("rustdoc", target_compiler.host));
             let _ = fs::remove_file(&bin_rustdoc);
             builder.copy(&tool_rustdoc, &bin_rustdoc);