Differentiation: make the build work without early-swift-driver

Windows does not have the early swift-driver. Disable CMP0157 for
compatibility.

Author: compnerd

Runtimes/Supplemental/Differentiation/CMakeLists.txt

@@ -1,4 +1,13 @@
 cmake_minimum_required(VERSION 3.29)
+# TODO before requiring CMake 4.1 or later
+# and/or enforcing CMP0195, please check/update
+# the implementation  of `emit_swift_interface`
+# in `EmitSwiftInterface.cmake`
+# to ensure it keeps laying down nested swiftmodule folders
+
+if(POLICY CMP0157 AND CMAKE_Swift_COMPILER_USE_OLD_DRIVER)
+  cmake_policy(SET CMP0157 OLD)
+endif()
 
 if($ENV{BUILD_NUMBER})
   math(EXPR BUILD_NUMBER "$ENV{BUILD_NUMBER} % 65535")