Fix hash-stable-is-unstable test

src/test/ui-fulldeps/hash-stable-is-unstable.stderr

@@ -2,7 +2,7 @@ error[E0601]: `main` function not found in crate `hash_stable_is_unstable`
    |
    = note: consider adding a `main` function to `$DIR/hash-stable-is-unstable.rs`
 
-error[E0658]: use of unstable library feature 'rustc_private': this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via `Cargo.toml` instead?
+error[E0658]: use of unstable library feature 'rustc_private': crate "rustc_data_structures" is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via `Cargo.toml` instead? (see issue #27812)
   --> $DIR/hash-stable-is-unstable.rs:3:1
    |
 LL | extern crate rustc_data_structures;
@@ -11,7 +11,7 @@ LL | extern crate rustc_data_structures;
    = note: for more information, see https://github.com/rust-lang/rust/issues/27812
    = help: add `#![feature(rustc_private)]` to the crate attributes to enable
 
-error[E0658]: use of unstable library feature 'rustc_private': this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via `Cargo.toml` instead?
+error[E0658]: use of unstable library feature 'rustc_private': crate "rustc" is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via `Cargo.toml` instead? (see issue #27812)
   --> $DIR/hash-stable-is-unstable.rs:5:1
    |
 LL | extern crate rustc;
@@ -20,7 +20,7 @@ LL | extern crate rustc;
    = note: for more information, see https://github.com/rust-lang/rust/issues/27812
    = help: add `#![feature(rustc_private)]` to the crate attributes to enable
 
-error[E0658]: use of unstable library feature 'rustc_private': this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via `Cargo.toml` instead?
+error[E0658]: use of unstable library feature 'rustc_private': crate "rustc_macros" is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via `Cargo.toml` instead? (see issue #27812)
   --> $DIR/hash-stable-is-unstable.rs:7:1
    |
 LL | extern crate rustc_macros;
@@ -29,7 +29,7 @@ LL | extern crate rustc_macros;
    = note: for more information, see https://github.com/rust-lang/rust/issues/27812
    = help: add `#![feature(rustc_private)]` to the crate attributes to enable
 
-error[E0658]: use of unstable library feature 'rustc_private': this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via `Cargo.toml` instead?
+error[E0658]: use of unstable library feature 'rustc_private': crate "rustc_macros" is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via `Cargo.toml` instead? (see issue #27812)
   --> $DIR/hash-stable-is-unstable.rs:10:5
    |
 LL | use rustc_macros::HashStable;
@@ -38,7 +38,7 @@ LL | use rustc_macros::HashStable;
    = note: for more information, see https://github.com/rust-lang/rust/issues/27812
    = help: add `#![feature(rustc_private)]` to the crate attributes to enable
 
-error[E0658]: use of unstable library feature 'rustc_private': this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via `Cargo.toml` instead?
+error[E0658]: use of unstable library feature 'rustc_private': crate "rustc_data_structures" is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via `Cargo.toml` instead? (see issue #27812)
   --> $DIR/hash-stable-is-unstable.rs:13:10
    |
 LL | #[derive(HashStable)]
@@ -47,7 +47,15 @@ LL | #[derive(HashStable)]
    = note: for more information, see https://github.com/rust-lang/rust/issues/27812
    = help: add `#![feature(rustc_private)]` to the crate attributes to enable
 
-error: aborting due to 6 previous errors
+error[E0658]: use of unstable library feature 'rustc_private': crate "rustc" is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via `Cargo.toml` instead? (see issue #27812)
+  --> $DIR/hash-stable-is-unstable.rs:13:10
+   |
+LL | #[derive(HashStable)]
+   |          ^^^^^^^^^^
+   |
+   = help: add #![feature(rustc_private)] to the crate attributes to enable
+
+error: aborting due to 7 previous errors
 
-Some errors have detailed explanations: E0601, E0658.
+Some errors occurred: E0601, E0658.
 For more information about an error, try `rustc --explain E0601`.