Add EmbeddedBook to test list in bootstrap

src/bootstrap/builder.rs

@@ -400,6 +400,7 @@ fn get_step_descriptions(kind: Kind) -> Vec<StepDescription> {
                 test::TheBook,
                 test::UnstableBook,
                 test::RustcBook,
+                test::EmbeddedBook,
                 test::Rustfmt,
                 test::Miri,
                 test::Clippy,