Revert "Revert "Don't load all extern crates unconditionally""

This reverts commit 5f0c54db4e.

src/test/rustdoc-ui/auxiliary/panic-item.rs

@@ -0,0 +1,17 @@
+// no-prefer-dynamic
+#![crate_type = "lib"]
+#![no_std]
+#![feature(lang_items)]
+
+use core::panic::PanicInfo;
+use core::sync::atomic::{self, Ordering};
+
+#[panic_handler]
+fn panic(_info: &PanicInfo) -> ! {
+    loop {
+        atomic::compiler_fence(Ordering::SeqCst);
+    }
+}
+
+#[lang = "eh_personality"]
+fn foo() {}

src/test/rustdoc-ui/unused-extern-crate.rs

@@ -0,0 +1,3 @@
+// check-pass
+// aux-crate:panic_item=panic-item.rs
+// @has unused_extern_crate/index.html

src/test/rustdoc/auxiliary/issue-66159-1.rs

@@ -1,2 +0,0 @@
-/// This will be referred to by the test docstring
-pub struct Something;

src/test/rustdoc/intra-doc/issue-66159.rs

@@ -1,4 +1,4 @@
-// aux-crate:priv:issue_66159_1=issue-66159-1.rs
+// aux-crate:priv:pub_struct=pub-struct.rs
 // compile-flags:-Z unstable-options
 
 // The issue was an ICE which meant that we never actually generated the docs
@@ -7,4 +7,4 @@
 // verify that the struct is linked correctly.
 
 // @has issue_66159/index.html
-//! [issue_66159_1::Something]
+//! [pub_struct::SomeStruct]