Add missing license header to CMake filewq

Author: owenv

cmake/modules/SwiftBuildConfig.cmake.in

@@ -1,3 +1,14 @@
+##===----------------------------------------------------------------------===##
+##
+## This source file is part of the Swift open source project
+##
+## Copyright (c) YEARS Apple Inc. and the Swift project authors
+## Licensed under Apache License v2.0 with Runtime Library Exception
+##
+## See http://swift.org/LICENSE.txt for license information
+## See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+##
+##===----------------------------------------------------------------------===##
 if(NOT TARGET SwiftBuild::SwiftBuild)
   include(@SWIFTBUILD_EXPORTS_FILE@)
 endif()