swift

026fcd24 - [ScanDependency][canImport] Improve canImport handling in explicit build

[ScanDependency][canImport] Improve canImport handling in explicit build Teach dependency scanner to report all the module canImport check result to swift-frontend, so swift-frontend doesn't need to parse swiftmodule or parse TBD file to determine the versions. This ensures dependency scanner and swift-frontend will have the same resolution for all canImport checks. This also fixes two related issues: * Previously, in order to get consistant results between scanner and frontend, scanner will request building the module in canImport check even it is not imported later. This slightly alters the definition of the canImport to only succeed when the module can be found AND be built. This also can affect the auto-link in such cases. * For caching build, the location of the clang module is abstracted away so swift-frontend cannot locate the TBD file to resolve underlyingVersion. rdar://128067152