DummyFramework.framework has two different properties to support two different kinds of test cases: to support ModuleInterface/build-alternative-interface-framework.swift, its macOS interfaces are broken, but to support ModuleInterface/arm64e-fallback.swift, it supports only arm64, not arm64e, on iOS. The arm64e test's behavior is about to change, which will complicate all of this. As a preliminary step, make the two tests use two different frameworks so they aren't so intertwined.
This temporarily keeps the arm64e test using the name "DummyFramework", but that will change.
This mechanism allows the compiler to use a backup interface file to build into a binary module when
a corresponding interface file from the SDK is failing for whatever reasons. This mechansim should be entirely opaque
to end users except several diagnostic messages communicating backup interfaces are used.
Part of rdar://77676064