Auto merge of #1736 - DJMcNab:rust-analyzer-private, r=RalfJung

Opt-in to rustc_private for `rust-analyzer`

rust-lang/rust-analyzer#7891

Author: bors

Cargo.toml

@@ -40,3 +40,8 @@ libc = "0.2"
 compiletest_rs = { version = "0.5", features = ["tmp"] }
 rustc_version = "0.2.3"
 colored = "2"
+
+[package.metadata.rust-analyzer]
+# This crate uses #[feature(rustc_private)]. 
+# See https://github.com/rust-analyzer/rust-analyzer/pull/7891
+rustc_private = true