Fix generating rustc docs with non-default lib directory.

src/bootstrap/builder.rs

@@ -710,15 +710,15 @@ impl<'a> Builder<'a> {
 
     /// Adds the compiler's directory of dynamic libraries to `cmd`'s dynamic
     /// library lookup path.
-    pub fn add_rustc_lib_path(&self, compiler: Compiler, cmd: &mut Cargo) {
+    pub fn add_rustc_lib_path(&self, compiler: Compiler, cmd: &mut Command) {
         // Windows doesn't need dylib path munging because the dlls for the
         // compiler live next to the compiler and the system will find them
         // automatically.
         if cfg!(windows) {
             return;
         }
 
-        add_dylib_path(vec![self.rustc_libdir(compiler)], &mut cmd.command);
+        add_dylib_path(vec![self.rustc_libdir(compiler)], cmd);
     }
 
     /// Gets a path to the compiler specified.
@@ -1515,6 +1515,10 @@ impl Cargo {
         self.command.env(key.as_ref(), value.as_ref());
         self
     }
+
+    pub fn add_rustc_lib_path(&mut self, builder: &Builder<'_>, compiler: Compiler) {
+        builder.add_rustc_lib_path(compiler, &mut self.command);
+    }
 }
 
 impl From<Cargo> for Command {

src/bootstrap/doc.rs

@@ -766,6 +766,10 @@ impl Step for RustcBook {
         if builder.config.verbose() {
             cmd.arg("--verbose");
         }
+        // If the lib directories are in an unusual location (changed in
+        // config.toml), then this needs to explicitly update the dylib search
+        // path.
+        builder.add_rustc_lib_path(self.compiler, &mut cmd);
         builder.run(&mut cmd);
         // Run rustbook/mdbook to generate the HTML pages.
         builder.ensure(RustbookSrc {

src/bootstrap/test.rs

@@ -270,7 +270,7 @@ impl Step for Rls {
             &[],
         );
 
-        builder.add_rustc_lib_path(compiler, &mut cargo);
+        cargo.add_rustc_lib_path(builder, compiler);
         cargo.arg("--").args(builder.config.cmd.test_args());
 
         if try_run(builder, &mut cargo.into()) {
@@ -328,7 +328,7 @@ impl Step for Rustfmt {
         t!(fs::create_dir_all(&dir));
         cargo.env("RUSTFMT_TEST_DIR", dir);
 
-        builder.add_rustc_lib_path(compiler, &mut cargo);
+        cargo.add_rustc_lib_path(builder, compiler);
 
         if try_run(builder, &mut cargo.into()) {
             builder.save_toolstate("rustfmt", ToolState::TestPass);
@@ -449,7 +449,7 @@ impl Step for Miri {
 
             cargo.arg("--").args(builder.config.cmd.test_args());
 
-            builder.add_rustc_lib_path(compiler, &mut cargo);
+            cargo.add_rustc_lib_path(builder, compiler);
 
             if !try_run(builder, &mut cargo.into()) {
                 return;
@@ -554,7 +554,7 @@ impl Step for Clippy {
 
         cargo.arg("--").args(builder.config.cmd.test_args());
 
-        builder.add_rustc_lib_path(compiler, &mut cargo);
+        cargo.add_rustc_lib_path(builder, compiler);
 
         builder.run(&mut cargo.into());
     }

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

@@ -402,9 +402,12 @@ fn generate_lint_output(
                 None => {
                     let rendered: Vec<&str> =
                         msgs.iter().filter_map(|msg| msg["rendered"].as_str()).collect();
+                    let non_json: Vec<&str> =
+                        stderr.lines().filter(|line| !line.starts_with('{')).collect();
                     Err(format!(
-                        "did not find lint `{}` in output of example, got:\n{}",
+                        "did not find lint `{}` in output of example, got:\n{}\n{}",
                         name,
+                        non_json.join("\n"),
                         rendered.join("\n")
                     )
                     .into())