CMP0025: Remove support for OLD behavior

Modules/Compiler/Clang-C.cmake

@@ -1,11 +1,6 @@
 include(Compiler/Clang)
 __compiler_clang(C)
 
-cmake_policy(GET CMP0025 appleClangPolicy)
-if(APPLE AND NOT appleClangPolicy STREQUAL NEW)
-  return()
-endif()
-
 if("x${CMAKE_C_COMPILER_FRONTEND_VARIANT}" STREQUAL "xMSVC")
   set(CMAKE_C_COMPILE_OPTIONS_EXPLICIT_LANGUAGE -TC)
   set(CMAKE_C_CLANG_TIDY_DRIVER_MODE "cl")

Modules/Compiler/Clang-CXX.cmake

@@ -15,11 +15,6 @@ if("x${CMAKE_CXX_COMPILER_FRONTEND_VARIANT}" STREQUAL "xGNU")
   set(CMAKE_CXX_COMPILE_OPTIONS_VISIBILITY_INLINES_HIDDEN "-fvisibility-inlines-hidden")
 endif()
 
-cmake_policy(GET CMP0025 appleClangPolicy)
-if(APPLE AND NOT appleClangPolicy STREQUAL NEW)
-  return()
-endif()
-
 if("x${CMAKE_CXX_COMPILER_FRONTEND_VARIANT}" STREQUAL "xMSVC")
   set(CMAKE_CXX_CLANG_TIDY_DRIVER_MODE "cl")
   set(CMAKE_CXX_INCLUDE_WHAT_YOU_USE_DRIVER_MODE "cl")