session: disable internal lints for rustdoc

If an internal lint uses `typeck_results` or similar queries then that
can result in rustdoc checking code that it shouldn't (e.g. from other
platforms) and emit compilation errors.

Signed-off-by: David Wood <david.wood@huawei.com>

src/librustdoc/lib.rs

@@ -788,7 +788,7 @@ fn main_options(options: config::Options) -> MainResult {
         if sess.opts.describe_lints {
             let mut lint_store = rustc_lint::new_lint_store(
                 sess.opts.unstable_opts.no_interleave_lints,
-                sess.unstable_options(),
+                sess.enable_internal_lints(),
             );
             let registered_lints = if let Some(register_lints) = compiler.register_lints() {
                 register_lints(sess, &mut lint_store);