bootstrap: reorganize lib.rs module decl and import/re-exports.

Make it easier to tell which import/re-export comes from what.

src/bootstrap/src/lib.rs

@@ -16,6 +16,9 @@
 //! More documentation can be found in each respective module below, and you can
 //! also check out the `src/bootstrap/README.md` file for more information.
 
+mod core;
+mod utils;
+
 use std::cell::{Cell, RefCell};
 use std::collections::{BTreeSet, HashMap, HashSet};
 use std::fmt::Display;
@@ -30,26 +33,20 @@ use build_helper::ci::gha;
 use build_helper::exit;
 use sha2::digest::Digest;
 use termcolor::{ColorChoice, StandardStream, WriteColor};
-use utils::channel::GitInfo;
-use utils::helpers::hex_encode;
 
+pub use self::core::builder::PathSet;
+pub use self::core::config::Config;
+pub use self::core::config::flags::{Flags, Subcommand};
 use crate::core::builder;
 use crate::core::builder::{Builder, Kind};
 use crate::core::config::{DryRun, LldMode, LlvmLibunwind, Target, TargetSelection, flags};
+pub use crate::utils::change_tracker::{
+    CONFIG_CHANGE_HISTORY, find_recent_config_change_ids, human_readable_changes,
+};
+use crate::utils::channel::GitInfo;
 use crate::utils::exec::{BehaviorOnFailure, BootstrapCommand, CommandOutput, OutputMode, command};
 use crate::utils::helpers::{
-    self, dir_is_empty, exe, libdir, mtime, output, set_file_times, symlink_dir,
-};
-
-mod core;
-mod utils;
-
-pub use core::builder::PathSet;
-pub use core::config::Config;
-pub use core::config::flags::{Flags, Subcommand};
-
-pub use utils::change_tracker::{
-    CONFIG_CHANGE_HISTORY, find_recent_config_change_ids, human_readable_changes,
+    self, dir_is_empty, exe, hex_encode, libdir, mtime, output, set_file_times, symlink_dir,
 };
 
 const LLVM_TOOLS: &[&str] = &[