Rollup merge of #129957 - chenx97:lint-docs-linker-opt, r=albertlarsan68

forward linker option to lint-docs

This fixes an error found when building the doc for a cross-built toolchain.

```
warning: the code example in lint `unstable_syntax_pre_expansion` in /buildroots/chenx97/rustc-1.80.1-src/compiler/rustc_lint_defs/src/builtin.rs failed to generate the expected output: did not find lint `unstable_syntax_p
re_expansion` in output of example, got:

error: linking with `cc` failed: exit status: 1
...
```
Closes: #129956

src/bootstrap/src/core/build_steps/doc.rs

@@ -1186,6 +1186,9 @@ impl Step for RustcBook {
         cmd.arg("--rustc");
         cmd.arg(&rustc);
         cmd.arg("--rustc-target").arg(self.target.rustc_target_arg());
+        if let Some(target_linker) = builder.linker(self.target) {
+            cmd.arg("--rustc-linker").arg(target_linker);
+        }
         if builder.is_verbose() {
             cmd.arg("--verbose");
         }

src/tools/lint-docs/src/lib.rs

@@ -56,6 +56,8 @@ pub struct LintExtractor<'a> {
     pub rustc_path: &'a Path,
     /// The target arch to build the docs for.
     pub rustc_target: &'a str,
+    /// The target linker overriding `rustc`'s default
+    pub rustc_linker: Option<&'a str>,
     /// Verbose output.
     pub verbose: bool,
     /// Validate the style and the code example.
@@ -459,6 +461,9 @@ impl<'a> LintExtractor<'a> {
         }
         cmd.arg("--error-format=json");
         cmd.arg("--target").arg(self.rustc_target);
+        if let Some(target_linker) = self.rustc_linker {
+            cmd.arg(format!("-Clinker={target_linker}"));
+        }
         if options.contains(&"test") {
             cmd.arg("--test");
         }

src/tools/lint-docs/src/main.rs

@@ -27,6 +27,7 @@ fn doit() -> Result<(), Box<dyn Error>> {
     let mut out_path = None;
     let mut rustc_path = None;
     let mut rustc_target = None;
+    let mut rustc_linker = None;
     let mut verbose = false;
     let mut validate = false;
     while let Some(arg) = args.next() {
@@ -55,6 +56,12 @@ fn doit() -> Result<(), Box<dyn Error>> {
                     None => return Err("--rustc-target requires a value".into()),
                 };
             }
+            "--rustc-linker" => {
+                rustc_linker = match args.next() {
+                    Some(s) => Some(s),
+                    None => return Err("--rustc-linker requires a value".into()),
+                };
+            }
             "-v" | "--verbose" => verbose = true,
             "--validate" => validate = true,
             s => return Err(format!("unexpected argument `{}`", s).into()),
@@ -77,6 +84,7 @@ fn doit() -> Result<(), Box<dyn Error>> {
         out_path: &out_path.unwrap(),
         rustc_path: &rustc_path.unwrap(),
         rustc_target: &rustc_target.unwrap(),
+        rustc_linker: rustc_linker.as_deref(),
         verbose,
         validate,
     };