[Dependency Scanning] Resolve cross-import overlays relative to defining interface for prebuilt binary Swift dependencies

When the dependency scanner picks a pre-built binary module candidate for a given dependency, it needs to be able to attempt to resolve its cross-import overlays relative to the textual interface that the binary module was built from. For example, if a collection of binary modules are located in, and resolved as dependencies from, a pre-built module directory, the scanner must lookup their corresponding cross-import overlays relative to the defining interface as read out from the binary module's MODULE_INTERFACE_PATH. https://github.com/swiftlang/swift/pull/70817 ensures that binary modules serialize the path to their defining textual interface.

Resolves rdar://130778577

lib/Serialization/SerializedModuleLoader.cpp

@@ -511,11 +511,16 @@ SerializedModuleLoaderBase::scanModuleFile(Twine modulePath, bool isFramework,
                                           LibraryKind::Framework));
   }
 
+  // Attempt to resolve the module's defining .swiftinterface path
+  std::string definingModulePath =
+       loadedModuleFile->resolveModuleDefiningFilePath(Ctx.SearchPathOpts.getSDKPath());
+
   // Map the set of dependencies over to the "module dependencies".
   auto dependencies = ModuleDependencyInfo::forSwiftBinaryModule(
       modulePath.str(), moduleDocPath, sourceInfoPath, moduleImports,
-      optionalModuleImports, linkLibraries, importedHeader, isFramework,
-      loadedModuleFile->isStaticLibrary(), /*module-cache-key*/ "");
+      optionalModuleImports, linkLibraries, importedHeader,
+      definingModulePath, isFramework, loadedModuleFile->isStaticLibrary(),
+      /*module-cache-key*/ "");
 
   return std::move(dependencies);
 }