test: Make a dedicated testsuite for rustfix

This commit adds a dedicated mode to compiletest for running rustfix tests,
adding a new `src/test/rustfix` directory which will execute all tests as a
"rustfix" test, namely requiring that a `*.fixed` is next to the main file which
is the result of the rustfix project's application of fixes.

The `rustfix` crate is pulled in to actually perform the fixing, and the rustfix
compiletest mode will assert a few properties about the fixing:

* The expected fixed output must be the same as rustc's output suggestions
  applied to the original code.
* The fixed code must compile successfully
* The fixed code must have no further diagnostics emitted about it

1 files changed, 1 insertions, 1 deletions

diff --git a/src/bootstrap/builder.rs b/src/bootstrap/builder.rs
index 08bb8ab4815..5920e356bca 100644
--- a/src/bootstrap/builder.rs
+++ b/src/bootstrap/builder.rs
@@ -326,7 +326,7 @@ impl<'a> Builder<'a> {
                 test::TheBook, test::UnstableBook, test::RustcBook,
                 test::Rustfmt, test::Miri, test::Clippy, test::RustdocJS, test::RustdocTheme,
                 // Run run-make last, since these won't pass without make on Windows
-                test::RunMake, test::RustdocUi),
+                test::RunMake, test::RustdocUi, test::Rustfix),
             Kind::Bench => describe!(test::Crate, test::CrateLibrustc),
             Kind::Doc => describe!(doc::UnstableBook, doc::UnstableBookGen, doc::TheBook,
                 doc::Standalone, doc::Std, doc::Test, doc::WhitelistedRustc, doc::Rustc,