[OpenMP] Remove the workaround of passing "-x assembler-with-cpp" man…

…ually

By building the assembly with language ASM now (since
4072c8a and
cbaa359), this shouldn't be
needed any longer.

Differential Revision: https://reviews.llvm.org/D150701

openmp/runtime/cmake/LibompHandleFlags.cmake

@@ -80,7 +80,6 @@ endfunction()
 # Assembler flags
 function(libomp_get_asmflags asmflags)
   set(asmflags_local)
-  libomp_append(asmflags_local "-x assembler-with-cpp" LIBOMP_HAVE_X_ASSEMBLER_WITH_CPP_FLAG)
   # Architectural assembler flags
   if(${IA32})
     if(CMAKE_SIZEOF_VOID_P EQUAL 8)

openmp/runtime/cmake/config-ix.cmake

@@ -96,11 +96,6 @@ if(WIN32)
       )
     endforeach()
   endforeach()
-else()
-  # It is difficult to create a dummy assembly file that compiles into an
-  # executable for every architecture and then check the C compiler to
-  # see if -x assembler-with-cpp exists and works, so we assume it does for non-Windows.
-  set(LIBOMP_HAVE_X_ASSEMBLER_WITH_CPP_FLAG TRUE)
 endif()
 if(${LIBOMP_FORTRAN_MODULES})
   libomp_check_fortran_flag(-m32 LIBOMP_HAVE_M32_FORTRAN_FLAG)