fix: Failing tests on rustc nightly (#15679)

Fixes #15678

Author: epage

tests/testsuite/custom_target.rs

@@ -11,8 +11,18 @@ const MINIMAL_LIB: &str = r#"
 #![feature(lang_items)]
 #![no_core]
 
+#[lang = "pointee_sized"]
+pub trait PointeeSized {
+    // Empty.
+}
+
+#[lang = "meta_sized"]
+pub trait MetaSized: PointeeSized {
+    // Empty.
+}
+
 #[lang = "sized"]
-pub trait Sized {
+pub trait Sized: MetaSized {
     // Empty.
 }
 #[lang = "copy"]

tests/testsuite/doc.rs

@@ -815,8 +815,14 @@ fn doc_target() {
                 #![feature(no_core, lang_items)]
                 #![no_core]
 
+                #[lang = "pointee_sized"]
+                trait PointeeSized {}
+
+                #[lang = "meta_sized"]
+                trait MetaSized: PointeeSized {}
+
                 #[lang = "sized"]
-                trait Sized {}
+                trait Sized: MetaSized {}
 
                 extern {
                     pub static A: u32;