Always disable requiring Foundation for '@objc' when building/typechecking interfaces

Author: artemcm

lib/Frontend/CompilerInvocation.cpp

@@ -735,6 +735,11 @@ static bool ParseLangArgs(LangOptions &Opts, ArgList &Args,
                                OPT_disable_testable_attr_requires_testable_module)) {
     Opts.EnableTestableAttrRequiresTestableModule
       = A->getOption().matches(OPT_enable_testable_attr_requires_testable_module);
+  } else if (FrontendOpts.RequestedAction ==
+             FrontendOptions::ActionType::TypecheckModuleFromInterface ||
+	     FrontendOpts.RequestedAction ==
+             FrontendOptions::ActionType::CompileModuleFromInterface) {
+    Opts.EnableObjCAttrRequiresFoundation = false;
   }
 
   if (Args.getLastArg(OPT_debug_cycles))

test/ModuleInterface/ExplicitInterfaceObjC.swiftinterface

@@ -0,0 +1,13 @@
+// swift-interface-format-version: 1.0
+// swift-module-flags: -module-name ExplicitInterfaceObjC
+
+// REQUIRES: objc_interop, OS=macosx
+// RUN: %empty-directory(%t)
+
+// RUN: %target-swift-frontend -compile-module-from-interface -module-name ExplicitInterfaceObjC -explicit-interface-module-build -o %/t/ExplicitInterfaceObjC.swiftmodule %s -verify
+// RUN: %target-swift-frontend -typecheck-module-from-interface -module-name ExplicitInterfaceObjC -explicit-interface-module-build -o %/t/ExplicitInterfaceObjC.swiftmodule %s -verify
+import Swift
+
+final public class Foo {
+  @objc deinit
+}