Add compatibility to be included in libstd

Author: alexcrichton

Cargo.toml

@@ -10,3 +10,10 @@ documentation = "https://docs.rs/rustc-demangle"
 description = """
 Rust compiler symbol demangling.
 """
+
+[dependencies]
+core = { version = '1.0.0', optional = true, package = 'rustc-std-workspace-core' }
+compiler_builtins = { version = '0.1.2', optional = true }
+
+[features]
+rustc-dep-of-std = ['core', 'compiler_builtins']