Fix enabling wasm-component-ld to match other tools

It was [pointed out recently][comment] that enabling `wasm-component-ld`
as a host tool is different from other host tools. This commit refactors
the logic to match by deduplicating selection of when to build other
tools and then using the same logic for `wasm-component-ld`.

[comment]: #127866 (comment)

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

@@ -1912,7 +1912,7 @@ impl Step for Assemble {
         // 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.
-        if builder.build_wasm_component_ld() {
+        if builder.tool_enabled("wasm-component-ld") {
             let wasm_component_ld_exe =
                 builder.ensure(crate::core::build_steps::tool::WasmComponentLd {
                     compiler: build_compiler,

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

@@ -473,7 +473,7 @@ impl Step for Rustc {
                     );
                 }
             }
-            if builder.build_wasm_component_ld() {
+            if builder.tool_enabled("wasm-component-ld") {
                 let src_dir = builder.sysroot_libdir(compiler, host).parent().unwrap().join("bin");
                 let ld = exe("wasm-component-ld", compiler.host);
                 builder.copy_link(&src_dir.join(&ld), &dst_dir.join(&ld));

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

@@ -693,14 +693,7 @@ impl Step for Cargo {
 
     fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
         let builder = run.builder;
-        run.path("src/tools/cargo").default_condition(
-            builder.config.extended
-                && builder.config.tools.as_ref().map_or(
-                    true,
-                    // If `tools` is set, search list for this tool.
-                    |tools| tools.iter().any(|tool| tool == "cargo"),
-                ),
-        )
+        run.path("src/tools/cargo").default_condition(builder.tool_enabled("cargo"))
     }
 
     fn make_run(run: RunConfig<'_>) {
@@ -772,14 +765,7 @@ impl Step for RustAnalyzer {
 
     fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
         let builder = run.builder;
-        run.path("src/tools/rust-analyzer").default_condition(
-            builder.config.extended
-                && builder
-                    .config
-                    .tools
-                    .as_ref()
-                    .map_or(true, |tools| tools.iter().any(|tool| tool == "rust-analyzer")),
-        )
+        run.path("src/tools/rust-analyzer").default_condition(builder.tool_enabled("rust-analyzer"))
     }
 
     fn make_run(run: RunConfig<'_>) {
@@ -821,12 +807,8 @@ impl Step for RustAnalyzerProcMacroSrv {
         run.path("src/tools/rust-analyzer")
             .path("src/tools/rust-analyzer/crates/proc-macro-srv-cli")
             .default_condition(
-                builder.config.extended
-                    && builder.config.tools.as_ref().map_or(true, |tools| {
-                        tools.iter().any(|tool| {
-                            tool == "rust-analyzer" || tool == "rust-analyzer-proc-macro-srv"
-                        })
-                    }),
+                builder.tool_enabled("rust-analyzer")
+                    || builder.tool_enabled("rust-analyzer-proc-macro-srv"),
             )
     }
 
@@ -874,16 +856,8 @@ impl Step for LlvmBitcodeLinker {
 
     fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
         let builder = run.builder;
-        run.path("src/tools/llvm-bitcode-linker").default_condition(
-            builder.config.extended
-                && builder
-                    .config
-                    .tools
-                    .as_ref()
-                    .map_or(builder.build.unstable_features(), |tools| {
-                        tools.iter().any(|tool| tool == "llvm-bitcode-linker")
-                    }),
-        )
+        run.path("src/tools/llvm-bitcode-linker")
+            .default_condition(builder.tool_enabled("llvm-bitcode-linker"))
     }
 
     fn make_run(run: RunConfig<'_>) {

src/bootstrap/src/lib.rs

@@ -1407,16 +1407,17 @@ Executed at: {executed_at}"#,
         None
     }
 
-    /// Returns whether it's requested that `wasm-component-ld` is built as part
-    /// of the sysroot. This is done either with the `extended` key in
-    /// `config.toml` or with the `tools` set.
-    fn build_wasm_component_ld(&self) -> bool {
-        if self.config.extended {
-            return true;
+    /// Returns whether the specified tool is configured as part of this build.
+    ///
+    /// This requires that both the `extended` key is set and the `tools` key is
+    /// either unset or specifically contains the specified tool.
+    fn tool_enabled(&self, tool: &str) -> bool {
+        if !self.config.extended {
+            return false;
         }
         match &self.config.tools {
-            Some(set) => set.contains("wasm-component-ld"),
-            None => false,
+            Some(set) => set.contains(tool),
+            None => true,
         }
     }