message: Clarify when cargo detects changes
diff: @@ -323,7 +323,7 @@ cross-compiling, so keep that in consideration of the impact on compile time.
  When rebuilding a package, Cargo does not necessarily know if the build script
  needs to be run again. By default, it takes a conservative approach of always
  -re-running the build script if any file within the package is changed (or the
  +re-running the build script if any rust file within the package is changed (or the
  list of files controlled by the [`exclude` and `include` fields]). For most
  cases, this is not a good choice, so it is recommended that every build script
  emit at least one of the `rerun-if` instructions (described below). If these
  