etc: add RUSTC_BOOTSTRAP to rust-analyzer config

Fixes the problem reported in
rust-lang#112391 (comment)

Author: notriddle

src/bootstrap/setup.rs

@@ -32,6 +32,7 @@ static SETTINGS_HASHES: &[&str] = &[
     "56e7bf011c71c5d81e0bf42e84938111847a810eee69d906bba494ea90b51922",
     "af1b5efe196aed007577899db9dae15d6dbc923d6fa42fa0934e68617ba9bbe0",
     "3468fea433c25fff60be6b71e8a215a732a7b1268b6a83bf10d024344e140541",
+    "47d227f424bf889b0d899b9cc992d5695e1b78c406e183cd78eafefbe5488923",
 ];
 static RUST_ANALYZER_SETTINGS: &str = include_str!("../etc/rust_analyzer_settings.json");
 

src/etc/rust_analyzer_settings.json

@@ -31,5 +31,8 @@
         "--json-output"
     ],
     "rust-analyzer.cargo.sysrootSrc": "./library",
-    "rust-analyzer.rustc.source": "./Cargo.toml"
+    "rust-analyzer.rustc.source": "./Cargo.toml",
+    "rust-analyzer.cargo.extraEnv": {
+        "RUSTC_BOOTSTRAP": "1"
+    }
 }