Auto merge of #43454 - Mark-Simulacrum:rollup, r=Mark-Simulacrum

Rollup of 11 pull requests

- Successful merges: #43297, #43322, #43342, #43361, #43366, #43374, #43379, #43401, #43421, #43428, #43446
- Failed merges:

1 files changed, 15 insertions, 0 deletions

diff --git a/src/libsyntax/build.rs b/src/libsyntax/build.rs
new file mode 100644
index 00000000000..d39340c3326
--- /dev/null
+++ b/src/libsyntax/build.rs
@@ -0,0 +1,15 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+fn main() {
+    println!("cargo:rerun-if-changed=build.rs");
+    println!("cargo:rerun-if-env-changed=CFG_RELEASE_CHANNEL");
+    println!("cargo:rerun-if-env-changed=CFG_DISABLE_UNSTABLE_FEATURES");
+}