Make the rustc and rustdoc wrapper not depend on libbootstrap

This slightly improves compilation time by reducing linking time
(saving about a 1/10 of the the total compilation time after
changing rustbuild) and slightly reduces disk usage (from 16MB for
the rustc wrapper to 4MB).

src/bootstrap/bin/rustc.rs

@@ -15,6 +15,8 @@
 //! switching compilers for the bootstrap and for build scripts will probably
 //! never get replaced.
 
+include!("../dylib_util.rs");
+
 use std::env;
 use std::path::PathBuf;
 use std::process::{Child, Command};
@@ -50,11 +52,11 @@ fn main() {
 
     let rustc = env::var_os(rustc).unwrap_or_else(|| panic!("{:?} was not set", rustc));
     let libdir = env::var_os(libdir).unwrap_or_else(|| panic!("{:?} was not set", libdir));
-    let mut dylib_path = bootstrap::util::dylib_path();
+    let mut dylib_path = dylib_path();
     dylib_path.insert(0, PathBuf::from(&libdir));
 
     let mut cmd = Command::new(rustc);
-    cmd.args(&args).env(bootstrap::util::dylib_path_var(), env::join_paths(&dylib_path).unwrap());
+    cmd.args(&args).env(dylib_path_var(), env::join_paths(&dylib_path).unwrap());
 
     // Get the name of the crate we're compiling, if any.
     let crate_name =
@@ -161,7 +163,7 @@ fn main() {
         eprintln!(
             "{} command: {:?}={:?} {:?}",
             prefix,
-            bootstrap::util::dylib_path_var(),
+            dylib_path_var(),
             env::join_paths(&dylib_path).unwrap(),
             cmd,
         );

src/bootstrap/bin/rustdoc.rs

@@ -7,6 +7,8 @@ use std::ffi::OsString;
 use std::path::PathBuf;
 use std::process::Command;
 
+include!("../dylib_util.rs");
+
 fn main() {
     let args = env::args_os().skip(1).collect::<Vec<_>>();
     let rustdoc = env::var_os("RUSTDOC_REAL").expect("RUSTDOC_REAL was not set");
@@ -20,14 +22,14 @@ fn main() {
         Err(_) => 0,
     };
 
-    let mut dylib_path = bootstrap::util::dylib_path();
+    let mut dylib_path = dylib_path();
     dylib_path.insert(0, PathBuf::from(libdir.clone()));
 
     let mut cmd = Command::new(rustdoc);
     cmd.args(&args)
         .arg("--sysroot")
         .arg(&sysroot)
-        .env(bootstrap::util::dylib_path_var(), env::join_paths(&dylib_path).unwrap());
+        .env(dylib_path_var(), env::join_paths(&dylib_path).unwrap());
 
     // Force all crates compiled by this compiler to (a) be unstable and (b)
     // allow the `rustc_private` feature to link to other unstable crates
@@ -59,7 +61,7 @@ fn main() {
     if verbose > 1 {
         eprintln!(
             "rustdoc command: {:?}={:?} {:?}",
-            bootstrap::util::dylib_path_var(),
+            dylib_path_var(),
             env::join_paths(&dylib_path).unwrap(),
             cmd,
         );

src/bootstrap/dylib_util.rs

@@ -0,0 +1,28 @@
+// Various utilities for working with dylib paths.
+//
+// This file is meant to be included directly to avoid a dependency on the bootstrap library from
+// the rustc and rustdoc wrappers. This improves compilation time by reducing the linking time.
+
+/// Returns the environment variable which the dynamic library lookup path
+/// resides in for this platform.
+pub fn dylib_path_var() -> &'static str {
+    if cfg!(target_os = "windows") {
+        "PATH"
+    } else if cfg!(target_os = "macos") {
+        "DYLD_LIBRARY_PATH"
+    } else if cfg!(target_os = "haiku") {
+        "LIBRARY_PATH"
+    } else {
+        "LD_LIBRARY_PATH"
+    }
+}
+
+/// Parses the `dylib_path_var()` environment variable, returning a list of
+/// paths that are members of this lookup path.
+pub fn dylib_path() -> Vec<PathBuf> {
+    let var = match env::var_os(dylib_path_var()) {
+        Some(v) => v,
+        None => return vec![],
+    };
+    env::split_paths(&var).collect()
+}

src/bootstrap/util.rs

@@ -54,29 +54,7 @@ pub fn add_dylib_path(path: Vec<PathBuf>, cmd: &mut Command) {
     cmd.env(dylib_path_var(), t!(env::join_paths(list)));
 }
 
-/// Returns the environment variable which the dynamic library lookup path
-/// resides in for this platform.
-pub fn dylib_path_var() -> &'static str {
-    if cfg!(target_os = "windows") {
-        "PATH"
-    } else if cfg!(target_os = "macos") {
-        "DYLD_LIBRARY_PATH"
-    } else if cfg!(target_os = "haiku") {
-        "LIBRARY_PATH"
-    } else {
-        "LD_LIBRARY_PATH"
-    }
-}
-
-/// Parses the `dylib_path_var()` environment variable, returning a list of
-/// paths that are members of this lookup path.
-pub fn dylib_path() -> Vec<PathBuf> {
-    let var = match env::var_os(dylib_path_var()) {
-        Some(v) => v,
-        None => return vec![],
-    };
-    env::split_paths(&var).collect()
-}
+include!("dylib_util.rs");
 
 /// Adds a list of lookup paths to `cmd`'s link library lookup path.
 pub fn add_link_lib_path(path: Vec<PathBuf>, cmd: &mut Command) {