Don't export upstream monomorphizations from compiler-builtins

Author: saethlin

compiler/rustc_codegen_ssa/src/back/symbol_export.rs

@@ -399,6 +399,11 @@ fn upstream_monomorphizations_provider(
     let async_drop_in_place_fn_def_id = tcx.lang_items().async_drop_in_place_fn();
 
     for &cnum in cnums.iter() {
+        // Don't export upstream monomorphizations from compiler-builtins:
+        // https://github.com/rust-lang/rust/issues/150173
+        if tcx.is_compiler_builtins(cnum) {
+            continue;
+        }
         for (exported_symbol, _) in tcx.exported_generic_symbols(cnum).iter() {
             let (def_id, args) = match *exported_symbol {
                 ExportedSymbol::Generic(def_id, args) => (def_id, args),