rustbuild: Document many more parts of the build

This commit expands the bootstrap build system's `README.md` as well as ensuring
that all API documentation is present and up-to-date. Additionally a new
`config.toml.example` file is checked in with commented out versions of all
possible configuration values.

1 files changed, 9 insertions, 0 deletions

diff --git a/src/bootstrap/lib.rs b/src/bootstrap/lib.rs
index 3158a3ab058..ef6184d6ca7 100644
--- a/src/bootstrap/lib.rs
+++ b/src/bootstrap/lib.rs
@@ -8,10 +8,17 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+//! A small helper library shared between the build system's executables
+//!
+//! Currently this just has some simple utilities for modifying the dynamic
+//! library lookup path.
+
 use std::env;
 use std::ffi::OsString;
 use std::path::PathBuf;
 
+/// 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"
@@ -22,6 +29,8 @@ pub fn dylib_path_var() -> &'static str {
     }
 }
 
+/// 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> {
     env::split_paths(&env::var_os(dylib_path_var()).unwrap_or(OsString::new()))
         .collect()