CMakeDetermineCompilerId: Support versioned LLVM for Visual Studio.

Supports versioned LLVM toolsets like LLVM_v142, LLVM_v141,
LLVM_v141_xp, etc. for Visual Studio (2010 and later).

The name for versioned LLVM toolsets has "LLVM_" prefix
plus MSVC toolset name (i.e. v142, v141, v141_xp, etc.).

Fixes: #19203

Modules/CMakeDetermineCompilerId.cmake

@@ -189,7 +189,7 @@ Id flags: ${testflags} ${CMAKE_${lang}_COMPILER_ID_FLAGS_ALWAYS}
     set(id_platform ${CMAKE_VS_PLATFORM_NAME})
     set(id_lang "${lang}")
     set(id_PostBuildEvent_Command "")
-    if(CMAKE_VS_PLATFORM_TOOLSET MATCHES "^[Ll][Ll][Vv][Mm]$")
+    if(CMAKE_VS_PLATFORM_TOOLSET MATCHES "^[Ll][Ll][Vv][Mm](_v[0-9]+(_xp)?)?$")
       set(id_cl_var "ClangClExecutable")
     elseif(CMAKE_VS_PLATFORM_TOOLSET MATCHES "v[0-9]+_clang_.*")
       set(id_cl clang.exe)