Failures on [cfe] Create PrefixBuilder through fragments

[johnniwinther]

There are new test failures on [cfe] Create PrefixBuilder through fragments.

The tests

co19/LanguageFeatures/Parts-with-imports/scope_A03_t02 Crash (expected Pass)
co19/LanguageFeatures/Parts-with-imports/scope_A03_t03 Crash (expected Pass)
co19/LanguageFeatures/Parts-with-imports/scope_A03_t03 DartkCrash (expected Pass)
co19/LanguageFeatures/Parts-with-imports/scope_A05_t01 Crash (expected Pass)
co19/LanguageFeatures/Parts-with-imports/scope_A05_t01 DartkCrash (expected Pass)
co19/LanguageFeatures/Parts-with-imports/scope_A05_t02 Crash (expected Pass)
co19/LanguageFeatures/Parts-with-imports/scope_A05_t02 DartkCrash (expected Pass)
pkg/front_end/test/fasta/messages/CantUseDeferredPrefixAsConstant/part_wrapped_script Fail (expected Pass)
pkg/front_end/test/fasta/messages/ClassImplementsDeferredClass/part_wrapped_script Fail (expected Pass)
pkg/front_end/test/fasta/messages/DeferredExtensionImport/part_wrapped_script Fail (expected Pass)
pkg/front_end/test/fasta/messages/ExtendsDeferredClass/part_wrapped_script Fail (expected Pass)
pkg/front_end/test/fasta/messages/ExtensionTypeImplementsDeferred/part_wrapped_script Fail (expected Pass)
pkg/front_end/test/fasta/messages/MixinDeferredMixin/part_wrapped_script Fail (expected Pass)
pkg/front_end/test/fasta/messages/MixinSuperClassConstraintDeferredClass/part_wrapped_script Fail (expected Pass)

are failing on configurations

cfe-strong-linux
cfe-unittest-asserts-release-linux
cfe-weak-linux
dart2js-hostasserts-linux-chrome-unsound
dart2js-hostasserts-linux-d8
dart2js-linux-chrome
dart2wasm-asserts-linux-chrome
dart2wasm-linux-d8
ddc-linux-chrome
vm-aot-linux-release-x64
vm-mac-debug-arm64
vm-win-release-x64