Autogen: Add clang --target= flag to compiler predefines command

Respect the compiler target value `CMAKE_<LANG>_COMPILER_TARGET` in
`CMAKE_<LANG>_COMPILER_PREDEFINES_COMMAND`.

Issue: #18425

Modules/Compiler/Clang.cmake

@@ -33,6 +33,14 @@ else()
     set(CMAKE_${lang}_LINKER_WRAPPER_FLAG "-Xlinker" " ")
     set(CMAKE_${lang}_LINKER_WRAPPER_FLAG_SEP)
 
+    if(CMAKE_${lang}_COMPILER_TARGET)
+      if(CMAKE_${lang}_COMPILER_VERSION VERSION_LESS 3.4.0)
+        list(APPEND CMAKE_${lang}_COMPILER_PREDEFINES_COMMAND "-target" "${CMAKE_${lang}_COMPILER_TARGET}")
+      else()
+        list(APPEND CMAKE_${lang}_COMPILER_PREDEFINES_COMMAND "--target=${CMAKE_${lang}_COMPILER_TARGET}")
+      endif()
+    endif()
+
     set(_CMAKE_${lang}_IPO_SUPPORTED_BY_CMAKE YES)
     set(_CMAKE_${lang}_IPO_MAY_BE_SUPPORTED_BY_COMPILER YES)