IntelLLVM: Fix C/C++ standard level flags on Windows

In commit a90d2a9e (IntelLLVM: Add support for Intel LLVM-based
compilers, 2020-11-02, v3.20.0-rc1~89^2~20) we accidentally left out
activation of the C/C++ standard level selection logic when IntelLLVM is
targeting the MSVC ABI.

Fixes: #22388

Modules/Compiler/IntelLLVM-C.cmake

@@ -49,10 +49,6 @@ else()
   set(CMAKE_C11_EXTENSION_COMPILE_OPTION "")
 endif()
 
-if(NOT "x${CMAKE_C_SIMULATE_ID}" STREQUAL "xMSVC")
-  # FIXME: The compiler actually defaults to C17, but
-  # CMake does not yet model or detect that standard.
-  __compiler_check_default_language_standard(C 2020 11)
-else()
-  set(CMAKE_C_STANDARD_DEFAULT "")
-endif()
+# FIXME: The compiler actually defaults to C17, but
+# CMake does not yet model or detect that standard.
+__compiler_check_default_language_standard(C 2020 11)

Modules/Compiler/IntelLLVM-CXX.cmake

@@ -62,8 +62,4 @@ else()
   set(CMAKE_CXX20_EXTENSION_COMPILE_OPTION "-Qstd=c++20")
 endif()
 
-if(NOT "x${CMAKE_CXX_SIMULATE_ID}" STREQUAL "xMSVC")
-  __compiler_check_default_language_standard(CXX 2020 14)
-else()
-  set(CMAKE_CXX_STANDARD_DEFAULT "")
-endif()
+__compiler_check_default_language_standard(CXX 2020 14)