Add docs for the test crate with the std docs

If the compiler docs aren't going to include the test crate then it may as well be included with std.

src/bootstrap/doc.rs

@@ -512,7 +512,7 @@ impl Step for Test {
 
     fn should_run(run: ShouldRun) -> ShouldRun {
         let builder = run.builder;
-        run.krate("test").default_condition(builder.config.compiler_docs)
+        run.krate("test").default_condition(builder.build.config.docs)
     }
 
     fn make_run(run: RunConfig) {
@@ -555,6 +555,9 @@ impl Step for Test {
 
         let mut cargo = builder.cargo(compiler, Mode::Libtest, target, "doc");
         compile::test_cargo(build, &compiler, target, &mut cargo);
+
+        cargo.arg("--no-deps").arg("-p").arg("test");
+
         build.run(&mut cargo);
         cp_r(&my_out, &out);
     }