Cleanup dist::Bootstrap and add a simple test for it

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

@@ -2604,15 +2604,17 @@ impl Step for RustDev {
 
 /// Tarball intended for internal consumption to ease rustc/std development.
 ///
+/// It only packages the binaries that were already compiled when bootstrap itself was built.
+///
 /// Should not be considered stable by end users.
 #[derive(Clone, Debug, Eq, Hash, PartialEq)]
 pub struct Bootstrap {
-    pub target: TargetSelection,
+    target: TargetSelection,
 }
 
 impl Step for Bootstrap {
     type Output = Option<GeneratedTarball>;
-    const DEFAULT: bool = false;
+
     const IS_HOST: bool = true;
 
     fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
@@ -2639,6 +2641,10 @@ impl Step for Bootstrap {
 
         Some(tarball.generate())
     }
+
+    fn metadata(&self) -> Option<StepMetadata> {
+        Some(StepMetadata::dist("bootstrap", self.target))
+    }
 }
 
 /// Tarball containing a prebuilt version of the build-manifest tool, intended to be used by the

src/bootstrap/src/core/builder/tests.rs

@@ -1608,6 +1608,19 @@ mod snapshot {
         ");
     }
 
+    #[test]
+    fn dist_bootstrap() {
+        let ctx = TestCtx::new();
+        insta::assert_snapshot!(
+            ctx
+                .config("dist")
+                .path("bootstrap")
+                .render_steps(), @r"
+        [build] rustc 0 <host> -> RustInstaller 1 <host>
+        [dist] bootstrap <host>
+        ");
+    }
+
     #[test]
     fn check_compiler_no_explicit_stage() {
         let ctx = TestCtx::new();