CFE: macros/augment_concrete crashes on fuzzing

[jensjoha]

This will fail (possibly the status entry in pkg/front_end/testcases/strong.status has to be removed):

out/ReleaseX64/dart --enable-asserts pkg/front_end/test/fasta/strong_suite.dart -DsemiFuzz=true -- strong/macros/augment_concrete

A "normal compile" doesn't fail, but on fuzzing it does like this:

Compiled and got 1 libs
 -> invalidating [...]/pkg/front_end/testcases/macros/augment_concrete.dart
 -> and got 1 libs
Can't serialize, got 'root::[...]/pkg/front_end/testcases/macros/augment_concrete.dart::@methods::[...]/pkg/front_end/testcases/macros/augment_concrete.dart::_#topLevelMethod#augment0 is already bound to Reference to [...]/pkg/front_end/testcases/macros/augment_concrete.dart::@methods::[...]/pkg/front_end/testcases/macros/augment_concrete.dart::_#topLevelMethod#augment0 with node _#topLevelMethod#augment0 (Procedure:316957), trying to bind to Reference to _#topLevelMethod#augment0 with node _#topLevelMethod#augment0 (Procedure:317190)' from #0      CanonicalName.bindTo (package:kernel/canonical_name.dart:237:7)
#1      Procedure.bindCanonicalNames (package:kernel/ast.dart:3038:40)
#2      Library.ensureCanonicalNames (package:kernel/ast.dart:511:21)
#3      Component.computeCanonicalNamesForLibrary (package:kernel/ast.dart:14028:13)
#4      BinaryPrinter._computeCanonicalNames (package:kernel/binary/ast_to_binary.dart:557:19)
#5      BinaryPrinter.writeComponentFile.<anonymous closure> (package:kernel/binary/ast_to_binary.dart:576:7)
#6      Timeline.timeSync (dart:developer/timeline.dart:160:22)
#7      BinaryPrinter.writeComponentFile (package:kernel/binary/ast_to_binary.dart:574:14)
#8      FuzzCompiles.canSerialize ([...]/pkg/front_end/test/fasta/testing/suite.dart:1427:35)
#9      FuzzCompiles.performFileInvalidation ([...]/pkg/front_end/test/fasta/testing/suite.dart:1340:12)
<asynchronous suspension>
#10     FuzzCompiles.run ([...]/pkg/front_end/test/fasta/testing/suite.dart:1202:45)
<asynchronous suspension>
#11     ChainContext.run.doStep.<anonymous closure> (package:testing/src/chain.dart:196:22)
<asynchronous suspension>

Probably a reference has to be given somewhere.

/cc @johnniwinther