Auto merge of #40693 - frewsxcv:rollup, r=frewsxcv

Rollup of 10 pull requests

- Successful merges: #40229, #40312, #40332, #40502, #40556, #40576, #40667, #40671, #40681, #40685
- Failed merges:

Author: bors

.gitmodules

@@ -27,3 +27,6 @@
 [submodule "reference"]
 	path = src/doc/reference
 	url = https://github.com/rust-lang-nursery/reference.git
+[submodule "book"]
+	path = src/doc/book
+	url = https://github.com/rust-lang/book

src/bootstrap/check.rs

@@ -285,6 +285,16 @@ pub fn docs(build: &Build, compiler: &Compiler) {
             continue
         }
 
+        // The nostarch directory in the book is for no starch, and so isn't guaranteed to build.
+        // we don't care if it doesn't build, so skip it.
+        use std::ffi::OsStr;
+        let path: &OsStr = p.as_ref();
+        if let Some(path) = path.to_str() {
+            if path.contains("nostarch") {
+                continue;
+            }
+        }
+
         println!("doc tests for: {}", p.display());
         markdown_test(build, compiler, &p);
     }