Make sure submodules are checked out with x test

If the submodule is not checked out, then these tests would fail.

Author: ehuss

src/bootstrap/src/core/build_steps/test.rs

@@ -2257,7 +2257,12 @@ impl BookTest {
 }
 
 macro_rules! test_book {
-    ($($name:ident, $path:expr, $book_name:expr, default=$default:expr;)+) => {
+    ($(
+        $name:ident, $path:expr, $book_name:expr,
+        default=$default:expr
+        $(,submodules = $submodules:expr)?
+        ;
+    )+) => {
         $(
             #[derive(Debug, Clone, PartialEq, Eq, Hash)]
             pub struct $name {
@@ -2280,6 +2285,11 @@ macro_rules! test_book {
                 }
 
                 fn run(self, builder: &Builder<'_>) {
+                    $(
+                        for submodule in $submodules {
+                            builder.require_and_update_submodule(submodule, None);
+                        }
+                    )*
                     builder.ensure(BookTest {
                         compiler: self.compiler,
                         path: PathBuf::from($path),
@@ -2293,15 +2303,15 @@ macro_rules! test_book {
 }
 
 test_book!(
-    Nomicon, "src/doc/nomicon", "nomicon", default=false;
-    Reference, "src/doc/reference", "reference", default=false;
+    Nomicon, "src/doc/nomicon", "nomicon", default=false, submodules=["src/doc/nomicon"];
+    Reference, "src/doc/reference", "reference", default=false, submodules=["src/doc/reference"];
     RustdocBook, "src/doc/rustdoc", "rustdoc", default=true;
     RustcBook, "src/doc/rustc", "rustc", default=true;
-    RustByExample, "src/doc/rust-by-example", "rust-by-example", default=false;
-    EmbeddedBook, "src/doc/embedded-book", "embedded-book", default=false;
-    TheBook, "src/doc/book", "book", default=false;
+    RustByExample, "src/doc/rust-by-example", "rust-by-example", default=false, submodules=["src/doc/rust-by-example"];
+    EmbeddedBook, "src/doc/embedded-book", "embedded-book", default=false, submodules=["src/doc/embedded-book"];
+    TheBook, "src/doc/book", "book", default=false, submodules=["src/doc/book"];
     UnstableBook, "src/doc/unstable-book", "unstable-book", default=true;
-    EditionGuide, "src/doc/edition-guide", "edition-guide", default=false;
+    EditionGuide, "src/doc/edition-guide", "edition-guide", default=false, submodules=["src/doc/edition-guide"];
 );
 
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]