add a flag to codegen fn attrs for foreign items

compiler/rustc_codegen_ssa/src/back/symbol_export.rs

@@ -570,7 +570,7 @@ fn symbol_export_level(tcx: TyCtxt<'_>, sym_def_id: DefId) -> SymbolExportLevel
     // core/std/allocators/etc. For example symbols used to hook up allocation
     // are not considered for export
     let codegen_fn_attrs = tcx.codegen_fn_attrs(sym_def_id);
-    let is_extern = codegen_fn_attrs.contains_extern_indicator(tcx, sym_def_id);
+    let is_extern = codegen_fn_attrs.contains_extern_indicator();
     let std_internal =
         codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL);
 

compiler/rustc_codegen_ssa/src/codegen_attrs.rs

@@ -385,6 +385,8 @@ fn apply_overrides(tcx: TyCtxt<'_>, did: LocalDefId, codegen_fn_attrs: &mut Code
 
     // Foreign items by default use no mangling for their symbol name.
     if tcx.is_foreign_item(did) {
+        codegen_fn_attrs.flags |= CodegenFnAttrFlags::FOREIGN_ITEM;
+
         // There's a few exceptions to this rule though:
         if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL) {
             // * `#[rustc_std_internal_symbol]` mangles the symbol name in a special way