Auto merge of #32133 - alexcrichton:linkchecker, r=brson

Add a link validator to rustbuild

This commit was originally targeted at just adding a link checking script to the rustbuild system. This ended up snowballing a bit to extend rustbuild to be amenable to various tools we have as part of the build system in general.

There's a new `src/tools` directory which has a number of scripts/programs that are purely intended to be used as part of the build system and CI of this repository. This is currently inhabited by rustbook, the error index generator, and a new linkchecker script added as part of this PR. I suspect that more tools like compiletest, tidy scripts, snapshot scripts, etc will migrate their way into this directory over time.

The commit which adds the error index generator shows the steps necessary to add new tools to the build system, namely:

1. New steps are defined for building the tool and running the tool
2. The dependencies are configured
3. The steps are implemented

In terms of the link checker, these commits do a few things:

* A new `src/tools/linkchecker` script is added. This will read an entire documentation tree looking for broken relative links (HTTP links aren't followed yet).
* A large number of broken links throughout the documentation were fixed. Many of these were just broken when viewed from core as opposed to std, but were easily fixed.
* A few rustdoc bugs here and there were fixed

3 files changed, 17 insertions, 17 deletions

diff --git a/src/libstd/num/f32.rs b/src/libstd/num/f32.rs
index 7f57d6dc650..37053025924 100644
--- a/src/libstd/num/f32.rs
+++ b/src/libstd/num/f32.rs
@@ -262,7 +262,7 @@ impl f32 {
     ///
     /// assert!(abs_difference <= f32::EPSILON);
     /// ```
-    /// [floating-point]: ../../../../../reference.html#machine-types
+    /// [floating-point]: ../reference.html#machine-types
     #[unstable(feature = "float_extras", reason = "signature is undecided",
                issue = "27752")]
     #[inline]
diff --git a/src/libstd/num/f64.rs b/src/libstd/num/f64.rs
index a39311f7d10..446e22a20ad 100644
--- a/src/libstd/num/f64.rs
+++ b/src/libstd/num/f64.rs
@@ -206,7 +206,7 @@ impl f64 {
     ///
     /// assert!(abs_difference < 1e-10);
     /// ```
-    /// [floating-point]: ../../../../../reference.html#machine-types
+    /// [floating-point]: ../reference.html#machine-types
     #[unstable(feature = "float_extras", reason = "signature is undecided",
                issue = "27752")]
     #[inline]
diff --git a/src/libstd/primitive_docs.rs b/src/libstd/primitive_docs.rs
index 24e35b87bf2..65ed879c4ad 100644
--- a/src/libstd/primitive_docs.rs
+++ b/src/libstd/primitive_docs.rs
@@ -27,11 +27,11 @@
 /// assert!(!bool_val);
 /// ```
 ///
-/// [`assert!`]: std/macro.assert!.html
-/// [`if` conditionals]: ../../book/if.html
-/// [`BitAnd`]: ../ops/trait.BitAnd.html
-/// [`BitOr`]: ../ops/trait.BitOr.html
-/// [`Not`]: ../ops/trait.Not.html
+/// [`assert!`]: macro.assert!.html
+/// [`if` conditionals]: ../book/if.html
+/// [`BitAnd`]: ops/trait.BitAnd.html
+/// [`BitOr`]: ops/trait.BitOr.html
+/// [`Not`]: ops/trait.Not.html
 ///
 /// # Examples
 ///
@@ -54,7 +54,7 @@
 /// }
 /// ```
 ///
-/// Also, since `bool` implements the [`Copy`](../marker/trait.Copy.html) trait, we don't
+/// Also, since `bool` implements the [`Copy`](marker/trait.Copy.html) trait, we don't
 /// have to worry about the move semantics (just like the integer and float primitives).
 mod prim_bool { }
 
@@ -421,7 +421,7 @@ mod prim_str { }
 /// assert_eq!(tuple.2, 'c');
 /// ```
 ///
-/// For more about tuples, see [the book](../../book/primitive-types.html#tuples).
+/// For more about tuples, see [the book](../book/primitive-types.html#tuples).
 ///
 /// # Trait implementations
 ///
@@ -437,14 +437,14 @@ mod prim_str { }
 /// * [`Default`]
 /// * [`Hash`]
 ///
-/// [`Clone`]: ../clone/trait.Clone.html
-/// [`PartialEq`]: ../cmp/trait.PartialEq.html
-/// [`Eq`]: ../cmp/trait.Eq.html
-/// [`PartialOrd`]: ../cmp/trait.PartialOrd.html
-/// [`Ord`]: ../cmp/trait.Ord.html
-/// [`Debug`]: ../fmt/trait.Debug.html
-/// [`Default`]: ../default/trait.Default.html
-/// [`Hash`]: ../hash/trait.Hash.html
+/// [`Clone`]: clone/trait.Clone.html
+/// [`PartialEq`]: cmp/trait.PartialEq.html
+/// [`Eq`]: cmp/trait.Eq.html
+/// [`PartialOrd`]: cmp/trait.PartialOrd.html
+/// [`Ord`]: cmp/trait.Ord.html
+/// [`Debug`]: fmt/trait.Debug.html
+/// [`Default`]: default/trait.Default.html
+/// [`Hash`]: hash/trait.Hash.html
 ///
 /// Due to a temporary restriction in Rust's type system, these traits are only
 /// implemented on tuples of arity 32 or less. In the future, this may change.