remove strip-hidden pass from compiler doc generation

Author: euclio

src/bootstrap/doc.rs

@@ -531,7 +531,7 @@ impl Step for Rustc {
 
         // Build cargo command.
         let mut cargo = builder.cargo(compiler, Mode::Rustc, target, "doc");
-        cargo.env("RUSTDOCFLAGS", "--document-private-items --passes strip-hidden");
+        cargo.env("RUSTDOCFLAGS", "--document-private-items");
         compile::rustc_cargo(builder, &mut cargo, target);
 
         // Only include compiler crates, no dependencies of those, such as `libc`.