text: #
  # When allocating RWX memory, check whether we need to use /dev/zero
  # as the file descriptor or not.
  #
  AC_DEFUN([AC_NEED_DEV_ZERO_FOR_MMAP],
  [AC_CACHE_CHECK([if /dev/zero is needed for mmap],
  ac_cv_need_dev_zero_for_mmap,
  [if test "$llvm_cv_os_type" = "Interix" ; then
     ac_cv_need_dev_zero_for_mmap=yes
   else
     ac_cv_need_dev_zero_for_mmap=no
   fi
  ])
  if test "$ac_cv_need_dev_zero_for_mmap" = yes; then
    AC_DEFINE([NEED_DEV_ZERO_FOR_MMAP],[1],
     [Define if /dev/zero should be used when mapping RWX memory, or undefine if its not necessary])
  fi])
  