Auto merge of #160098 - camelid:bootstrap-doc-mergeable, r=<try>

bootstrap: Enable rustdoc mergeable CCI for std and internal docs


try-job: dist-x86_64-linux

Author: bors

src/bootstrap/src/core/builder/cargo.rs

@@ -663,6 +663,7 @@ impl Builder<'_> {
         }
 
         if cmd_kind == Kind::Doc {
+            cargo.arg("-Zrustdoc-mergeable-info");
             let my_out = match mode {
                 // This is the intended out directory for compiler documentation.
                 Mode::Rustc | Mode::ToolRustcPrivate | Mode::ToolBootstrap | Mode::ToolTarget => {