Prevent name collisions with internal implementation details

The implementation of the linkage attribute inside extern blocks defines
symbols starting with _rust_extern_with_linkage_. If someone tries to
also define this symbol you will get a symbol conflict or even an ICE.
By adding an unpredictable component to the symbol name, this becomes
less of an issue.

src/constant.rs

@@ -310,7 +310,10 @@ fn data_id_for_static(
         // `extern_with_linkage_foo` will instead be initialized to
         // zero.
 
-        let ref_name = format!("_rust_extern_with_linkage_{}", symbol_name);
+        let ref_name = format!(
+            "_rust_extern_with_linkage_{:016x}_{symbol_name}",
+            tcx.stable_crate_id(LOCAL_CRATE)
+        );
         let ref_data_id = module.declare_data(&ref_name, Linkage::Local, false, false).unwrap();
         let mut data = DataDescription::new();
         data.set_align(align);