Update comments

build.rs

@@ -4,11 +4,12 @@
 use std::env;
 
 fn main() {
+    // Depend on this file to prevent rebuilding on any change - see #1173 for details
+    println!("cargo:rerun-if-changed=build.rs");
+
     // Re-export $TARGET during the build so that our executable tests know
     // what environment variable CARGO_TARGET_@TARGET@_RUNNER to check when
     // they want to spawn off executables.
-
-    println!("cargo:rerun-if-changed=build.rs");
     let target = env::var("TARGET").unwrap();
     println!("cargo:rustc-env=TARGET={target}");
 }