Add -Zembed-metadata CLI option

compiler/rustc_interface/src/tests.rs

@@ -787,6 +787,7 @@ fn test_unstable_options_tracking_hash() {
     tracked!(direct_access_external_data, Some(true));
     tracked!(dual_proc_macros, true);
     tracked!(dwarf_version, Some(5));
+    tracked!(embed_metadata, false);
     tracked!(embed_source, true);
     tracked!(emit_thin_lto, false);
     tracked!(emscripten_wasm_eh, true);