Compile rustc_driver by default

src/bootstrap/doc.rs

@@ -667,7 +667,7 @@ impl Step for Rustc {
  /// Compiler documentation is distributed separately, so we make sure
  /// we do not merge it with the other documentation from std, test and
  /// proc_macros. This is largely just a wrapper around `cargo doc`.
- fn run(self, builder: &Builder<'_>) {
+ fn run(mut self, builder: &Builder<'_>) {
  let stage = self.stage;
  let target = self.target;
 
@@ -725,6 +725,11 @@ impl Step for Rustc {
  cargo.rustdocflag("ena=https://docs.rs/ena/latest/");
 
  let mut to_open = None;
+
+ if self.crates.is_empty() {
+ self.crates = INTERNER.intern_list(vec!["rustc_driver".to_owned()]);
+ };
+
  for krate in &*self.crates {
  // Create all crate output directories first to make sure rustdoc uses
  // relative links.