FujitsuClang: Use GNU-like command-line

Modules/CMakeDetermineCompilerId.cmake

@@ -223,6 +223,8 @@ function(CMAKE_DETERMINE_COMPILER_ID lang flagvar src)
     else()
       set(CMAKE_${lang}_COMPILER_FRONTEND_VARIANT "GNU")
     endif()
+  elseif("x${CMAKE_${lang}_COMPILER_ID}" STREQUAL "xFujitsuClang")
+    set(CMAKE_${lang}_COMPILER_FRONTEND_VARIANT "GNU")
   else()
     set(CMAKE_${lang}_COMPILER_FRONTEND_VARIANT "")
   endif()