Clang: Add MSVC frontend detection for the ASM compiler

Fixes: #22495

Modules/CMakeDetermineASMCompiler.cmake

@@ -125,6 +125,7 @@ if(NOT CMAKE_ASM${ASM_DIALECT}_COMPILER_ID)
   include(CMakeDetermineCompilerId)
   set(userflags)
   CMAKE_DETERMINE_COMPILER_ID_VENDOR(ASM${ASM_DIALECT} "${userflags}")
+  set(_variant "")
   if("x${CMAKE_ASM${ASM_DIALECT}_COMPILER_ID}" STREQUAL "xIAR")
     # primary necessary to detect architecture, so the right archiver and linker can be picked
     # eg. "IAR Assembler V8.10.1.12857/W32 for ARM" or "IAR Assembler V4.11.1.4666 for Renesas RX"
@@ -137,6 +138,19 @@ if(NOT CMAKE_ASM${ASM_DIALECT}_COMPILER_ID)
     if(_all_compileid_matches)
       list(GET _all_compileid_matches "-1" CMAKE_ASM${ASM_DIALECT}_COMPILER_ARCHITECTURE_ID)
     endif()
+  elseif("x${CMAKE_ASM${ASM_DIALECT}_COMPILER_ID}" STREQUAL "xClang")
+    # Test whether an MSVC-like command-line option works.
+    execute_process(COMMAND ${CMAKE_ASM${ASM_DIALECT}_COMPILER} -?
+      OUTPUT_VARIABLE _clang_output
+      ERROR_VARIABLE _clang_output
+      RESULT_VARIABLE _clang_result)
+      if(_clang_result EQUAL 0)
+        set(CMAKE_ASM${ASM_DIALECT}_COMPILER_FRONTEND_VARIANT "MSVC")
+        set(CMAKE_ASM${ASM_DIALECT}_SIMULATE_ID MSVC)
+      else()
+        set(CMAKE_ASM${ASM_DIALECT}_COMPILER_FRONTEND_VARIANT "GNU")
+      endif()
+      set(_variant " with ${CMAKE_ASM${ASM_DIALECT}_COMPILER_FRONTEND_VARIANT}-like command-line")
   endif()
 
   _cmake_find_compiler_sysroot(ASM${ASM_DIALECT})
@@ -144,6 +158,8 @@ if(NOT CMAKE_ASM${ASM_DIALECT}_COMPILER_ID)
   unset(CMAKE_ASM${ASM_DIALECT}_COMPILER_ID_OUTPUT)
   unset(_all_compileid_matches)
   unset(_compileid)
+  unset(_clang_result)
+  unset(_clang_output)
 endif()
 
 if(CMAKE_ASM${ASM_DIALECT}_COMPILER_ID)
@@ -157,9 +173,10 @@ if(CMAKE_ASM${ASM_DIALECT}_COMPILER_ID)
   else()
     set(_archid "")
   endif()
-  message(STATUS "The ASM${ASM_DIALECT} compiler identification is ${CMAKE_ASM${ASM_DIALECT}_COMPILER_ID}${_archid}${_version}")
+  message(STATUS "The ASM${ASM_DIALECT} compiler identification is ${CMAKE_ASM${ASM_DIALECT}_COMPILER_ID}${_archid}${_version}${_variant}")
   unset(_archid)
   unset(_version)
+  unset(_variant)
 else()
   message(STATUS "The ASM${ASM_DIALECT} compiler identification is unknown")
 endif()