Make WasmComponentLd a ToolTarget tool

This avoid needless rebuilds when the tool can be simply compiled by the stage0 compiler.

Author: Kobzol

src/bootstrap/src/core/build_steps/compile.rs

@@ -2282,15 +2282,13 @@ impl Step for Assemble {
         }
 
         // In addition to `rust-lld` also install `wasm-component-ld` when
-        // LLD is enabled. This is a relatively small binary that primarily
-        // delegates to the `rust-lld` binary for linking and then runs
-        // logic to create the final binary. This is used by the
-        // `wasm32-wasip2` target of Rust.
+        // is enabled. This is used by the `wasm32-wasip2` target of Rust.
         if builder.tool_enabled("wasm-component-ld") {
-            let wasm_component = builder.ensure(crate::core::build_steps::tool::WasmComponentLd {
-                compiler: build_compiler,
-                target: target_compiler.host,
-            });
+            let wasm_component =
+                builder.ensure(crate::core::build_steps::tool::WasmComponentLd::for_target(
+                    builder,
+                    target_compiler.host,
+                ));
             builder.copy_link(
                 &wasm_component.tool_path,
                 &libdir_bin.join(wasm_component.tool_path.file_name().unwrap()),

src/bootstrap/src/core/build_steps/tool.rs

@@ -534,7 +534,6 @@ bootstrap_tool!(
     // rustdoc-gui-test has a crate dependency on compiletest, so it needs the same unstable features.
     RustdocGUITest, "src/tools/rustdoc-gui-test", "rustdoc-gui-test", is_unstable_tool = true, allow_features = COMPILETEST_ALLOW_FEATURES;
     CoverageDump, "src/tools/coverage-dump", "coverage-dump";
-    WasmComponentLd, "src/tools/wasm-component-ld", "wasm-component-ld", is_unstable_tool = true, allow_features = "min_specialization";
     UnicodeTableGenerator, "src/tools/unicode-table-generator", "unicode-table-generator";
     FeaturesStatusDump, "src/tools/features-status-dump", "features-status-dump";
     OptimizedDist, "src/tools/opt-dist", "opt-dist", submodules = &["src/tools/rustc-perf"];
@@ -929,6 +928,63 @@ impl Step for LldWrapper {
     }
 }
 
+#[derive(Debug, Clone, Hash, PartialEq, Eq)]
+pub struct WasmComponentLd {
+    build_compiler: Compiler,
+    target: TargetSelection,
+}
+
+impl WasmComponentLd {
+    pub fn for_target(builder: &Builder<'_>, target: TargetSelection) -> Self {
+        Self { build_compiler: get_tool_target_compiler(builder, target), target }
+    }
+}
+
+impl Step for WasmComponentLd {
+    type Output = ToolBuildResult;
+
+    const ONLY_HOSTS: bool = true;
+
+    fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
+        run.path("src/tools/wasm-component-ld")
+    }
+
+    fn make_run(run: RunConfig<'_>) {
+        run.builder.ensure(WasmComponentLd {
+            build_compiler: get_tool_target_compiler(run.builder, run.target),
+            target: run.target,
+        });
+    }
+
+    #[cfg_attr(
+        feature = "tracing",
+        instrument(
+            level = "debug",
+            name = "WasmComponentLd::run",
+            skip_all,
+            fields(build_compiler = ?self.build_compiler),
+        ),
+    )]
+    fn run(self, builder: &Builder<'_>) -> ToolBuildResult {
+        builder.ensure(ToolBuild {
+            build_compiler: self.build_compiler,
+            target: self.target,
+            tool: "wasm-component-ld",
+            mode: Mode::ToolTarget,
+            path: "src/tools/wasm-component-ld",
+            source_type: SourceType::InTree,
+            extra_features: vec![],
+            allow_features: "min-specialization",
+            cargo_args: vec![],
+            artifact_kind: ToolArtifactKind::Binary,
+        })
+    }
+
+    fn metadata(&self) -> Option<StepMetadata> {
+        Some(StepMetadata::build("WasmComponentLd", self.target).built_by(self.build_compiler))
+    }
+}
+
 #[derive(Debug, Clone, Hash, PartialEq, Eq)]
 pub struct RustAnalyzer {
     pub compiler: Compiler,

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

@@ -980,6 +980,7 @@ impl<'a> Builder<'a> {
                 tool::CoverageDump,
                 tool::LlvmBitcodeLinker,
                 tool::RustcPerf,
+                tool::WasmComponentLd
             ),
             Kind::Clippy => describe!(
                 clippy::Std,

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

@@ -1021,7 +1021,6 @@ mod snapshot {
         [build] rustc 0 <host> -> WasmComponentLd 1 <host>
         [build] rustc 1 <host> -> std 1 <host>
         [build] rustc 1 <host> -> rustc 2 <host>
-        [build] rustc 1 <host> -> WasmComponentLd 2 <host>
         [build] rustdoc 1 <host>
         [doc] std 2 <host>
         [build] rustc 2 <host> -> std 2 <host>
@@ -1205,7 +1204,6 @@ mod snapshot {
         [build] rustc 0 <host> -> WasmComponentLd 1 <host>
         [build] rustc 1 <host> -> std 1 <host>
         [build] rustc 1 <host> -> rustc 2 <host>
-        [build] rustc 1 <host> -> WasmComponentLd 2 <host>
         [build] rustdoc 1 <host>
         [doc] std 2 <target1>
         [build] rustc 2 <host> -> std 2 <host>