Rollup merge of #137736 - bjorn3:compiler_builtins_export_fix, r=petrochenkov

Don't attempt to export compiler-builtins symbols from rust dylibs

They are marked with hidden visibility to prevent them from getting exported, so we shouldn't ask the linker to export them anyway. The only thing that does it cause a warning on macOS.

Part of #136096

cc `@jyn514`

Author: jhpratt

compiler/rustc_codegen_ssa/src/back/linker.rs

@@ -1782,7 +1782,10 @@ fn exported_symbols_for_non_proc_macro(tcx: TyCtxt<'_>, crate_type: CrateType) -
     let mut symbols = Vec::new();
     let export_threshold = symbol_export::crates_export_threshold(&[crate_type]);
     for_each_exported_symbols_include_dep(tcx, crate_type, |symbol, info, cnum| {
-        if info.level.is_below_threshold(export_threshold) {
+        // Do not export mangled symbols from cdylibs and don't attempt to export compiler-builtins
+        // from any cdylib. The latter doesn't work anyway as we use hidden visibility for
+        // compiler-builtins. Most linkers silently ignore it, but ld64 gives a warning.
+        if info.level.is_below_threshold(export_threshold) && !tcx.is_compiler_builtins(cnum) {
             symbols.push(symbol_export::exporting_symbol_name_for_instance_in_crate(
                 tcx, symbol, cnum,
             ));
@@ -1821,7 +1824,9 @@ pub(crate) fn linked_symbols(
 
     let export_threshold = symbol_export::crates_export_threshold(&[crate_type]);
     for_each_exported_symbols_include_dep(tcx, crate_type, |symbol, info, cnum| {
-        if info.level.is_below_threshold(export_threshold) || info.used {
+        if info.level.is_below_threshold(export_threshold) && !tcx.is_compiler_builtins(cnum)
+            || info.used
+        {
             symbols.push((
                 symbol_export::linking_symbol_name_for_instance_in_crate(tcx, symbol, cnum),
                 info.kind,