IntelLLVM: Use C23 and C++23 flags only versions supporting them

Revise commit 4331f7b4bf (IntelLLVM: Add provisional flags for C23 and
C++23, 2023-01-12, v3.26.0-rc1~86^2).

Modules/Compiler/IntelLLVM-C.cmake

@@ -42,8 +42,10 @@ if(NOT "x${CMAKE_C_SIMULATE_ID}" STREQUAL "xMSVC")
   set(CMAKE_C17_STANDARD_COMPILE_OPTION "-std=c17")
   set(CMAKE_C17_EXTENSION_COMPILE_OPTION "-std=gnu17")
 
-  set(CMAKE_C23_STANDARD_COMPILE_OPTION "-std=c2x")
-  set(CMAKE_C23_EXTENSION_COMPILE_OPTION "-std=gnu2x")
+  if(CMAKE_C_COMPILER_VERSION VERSION_GREATER_EQUAL 2022.1.0)
+    set(CMAKE_C23_STANDARD_COMPILE_OPTION "-std=c2x")
+    set(CMAKE_C23_EXTENSION_COMPILE_OPTION "-std=gnu2x")
+  endif()
 else()
   # clang-cl doesn't have any of these
   set(CMAKE_C90_STANDARD_COMPILE_OPTION "")
@@ -58,8 +60,10 @@ else()
   set(CMAKE_C17_STANDARD_COMPILE_OPTION "")
   set(CMAKE_C17_EXTENSION_COMPILE_OPTION "")
 
-  set(CMAKE_C23_STANDARD_COMPILE_OPTION "")
-  set(CMAKE_C23_EXTENSION_COMPILE_OPTION "")
+  if(CMAKE_C_COMPILER_VERSION VERSION_GREATER_EQUAL 2022.1.0)
+    set(CMAKE_C23_STANDARD_COMPILE_OPTION "")
+    set(CMAKE_C23_EXTENSION_COMPILE_OPTION "")
+  endif()
 endif()
 
 __compiler_check_default_language_standard(C 2020 17)

Modules/Compiler/IntelLLVM-CXX.cmake

@@ -47,8 +47,10 @@ if(NOT "x${CMAKE_CXX_SIMULATE_ID}" STREQUAL "xMSVC")
   set(CMAKE_CXX20_STANDARD_COMPILE_OPTION  "-std=c++20")
   set(CMAKE_CXX20_EXTENSION_COMPILE_OPTION "-std=gnu++20")
 
-  set(CMAKE_CXX23_STANDARD_COMPILE_OPTION  "-std=c++2b")
-  set(CMAKE_CXX23_EXTENSION_COMPILE_OPTION "-std=gnu++2b")
+  if(CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL 2021.2.0)
+    set(CMAKE_CXX23_STANDARD_COMPILE_OPTION  "-std=c++2b")
+    set(CMAKE_CXX23_EXTENSION_COMPILE_OPTION "-std=gnu++2b")
+  endif()
 else()
   set(CMAKE_CXX98_STANDARD_COMPILE_OPTION  "")
   set(CMAKE_CXX98_EXTENSION_COMPILE_OPTION "")
@@ -65,8 +67,10 @@ else()
   set(CMAKE_CXX20_STANDARD_COMPILE_OPTION  "-Qstd:c++20")
   set(CMAKE_CXX20_EXTENSION_COMPILE_OPTION "-Qstd:c++20")
 
-  set(CMAKE_CXX23_STANDARD_COMPILE_OPTION  "-Qstd:c++2b")
-  set(CMAKE_CXX23_EXTENSION_COMPILE_OPTION "-Qstd:c++2b")
+  if(CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL 2021.2.0)
+    set(CMAKE_CXX23_STANDARD_COMPILE_OPTION  "-Qstd:c++2b")
+    set(CMAKE_CXX23_EXTENSION_COMPILE_OPTION "-Qstd:c++2b")
+  endif()
 endif()
 
 __compiler_check_default_language_standard(CXX 2020 14)