Revert "[test] Put variadic definitions in a platform-independent header and remove the platform requirement."

The linux bots are still in oblivion of the variadic c function error.

Swift SVN r32915

Author: nkcsgexi

test/ClangModules/availability_variadic.swift

@@ -1,6 +1,8 @@
 // RUN: %target-swift-frontend(mock-sdk: %clang-importer-sdk) -parse -verify -I %S/Inputs/custom-modules %s
 
-import cfuncs
+// REQUIRES: OS=macosx
+
+import Foundation
 
 func variadicFunc2(A : Int32, _: Any...) -> Int { return 0 }
 

test/Inputs/clang-importer-sdk/usr/include/Foundation.h

@@ -981,3 +981,7 @@ typedef NS_OPTIONS(NSUInteger, NSEnumerationOptions) {
 @property (readonly) BOOL appliesForAJob;
 @property (readonly) BOOL setShouldBeInfinite;
 @end
+
+int variadicFunc1(int A, ...);
+
+int variadicFunc2(int A, ...);

test/Inputs/clang-importer-sdk/usr/include/cfuncs.h

@@ -42,5 +42,3 @@ struct not_importable;
 
 void opaque_pointer_param(struct not_importable *);
 
-int variadicFunc1(int A, ...);
-int variadicFunc2(int A, ...);