Reduce usage of buildUnsupported.

test/kernel/regression/unresolved_for_in.dart.txt

Index: test/kernel/regression/unresolved_for_in.dart.txt
diff --git a/test/kernel/regression/unresolved_for_in.dart.txt b/test/kernel/regression/unresolved_for_in.dart.txt
index 86d3c3224873c2879071020dfd11f192bfcc037d..e620c0d8cc26ab1776a88b69ed9f72a16022a786 100644
--- a/test/kernel/regression/unresolved_for_in.dart.txt
+++ b/test/kernel/regression/unresolved_for_in.dart.txt
@@ -16,7 +16,7 @@ class Fisk extends core::Object {
     }
     for(final #t4 in x) {
       let final #t5 = #t4 in invalid-expression;
-      core::print(throw "Kernel IR not yet implemented for 'handleError'.");
+      core::print(invalid-expression);
     }
     for(final #t6 in x) {
       let final #t7 = #t6 in invalid-expression;
@@ -40,7 +40,7 @@ static method main(dynamic arguments) → dynamic {
   }
   for(final #t14 in arguments) {
     let final #t15 = #t14 in invalid-expression;
-    core::print(throw "Kernel IR not yet implemented for 'handleError'.");
+    core::print(invalid-expression);
   }
   for(final #t16 in arguments) {
     let final #t17 = #t16 in invalid-expression;