bootstrap: add rustc-dev install target

Author: Nadrieril

src/bootstrap/src/core/build_steps/dist.rs

@@ -892,8 +892,8 @@ impl Step for Std {
 #[derive(Debug, Clone, Hash, PartialEq, Eq)]
 pub struct RustcDev {
     /// The compiler that will build rustc which will be shipped in this component.
-    build_compiler: Compiler,
-    target: TargetSelection,
+    pub build_compiler: Compiler,
+    pub target: TargetSelection,
 }
 
 impl RustcDev {

src/bootstrap/src/core/build_steps/install.rs

@@ -279,6 +279,17 @@ install!((self, builder, _config),
         });
         install_sh(builder, "rustc", self.build_compiler, Some(self.target), &tarball);
     };
+    RustcDev, alias = "rustc-dev", Self::should_build(_config), IS_HOST: true, {
+        if let Some(tarball) = builder.ensure(dist::RustcDev {
+            build_compiler: self.build_compiler, target: self.target
+        }) {
+            install_sh(builder, "rustc-dev", self.build_compiler, Some(self.target), &tarball);
+        } else {
+            builder.info(
+                &format!("skipping Install RustcDev stage{} ({})", self.build_compiler.stage + 1, self.target),
+            );
+        }
+    };
     RustcCodegenCranelift, alias = "rustc-codegen-cranelift", Self::should_build(_config), IS_HOST: true, {
         if let Some(tarball) = builder.ensure(dist::CraneliftCodegenBackend {
             compilers: RustcPrivateCompilers::from_build_compiler(builder, self.build_compiler, self.target),

src/bootstrap/src/core/builder/mod.rs

@@ -998,6 +998,7 @@ impl<'a> Builder<'a> {
                 // binary path, we must install rustc before the tools. Otherwise, the rust-installer will
                 // install the same binaries twice for each tool, leaving backup files (*.old) as a result.
                 install::Rustc,
+                install::RustcDev,
                 install::Cargo,
                 install::RustAnalyzer,
                 install::Rustfmt,