When building in debug mode for Windows on Arm, Clang reports the
following error without this patch:

  error: attribute 'dllexport' cannot be applied to member of
  'dllexport' class.

Change-Id: Ib3b12fce7daa368f9464b080ac7a7bce1ddd5370
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1611799Reviewed-by: Sigurd Schneider <sigurds@chromium.org>
Commit-Queue: Richard Townsend <richard.townsend@arm.com>
Cr-Commit-Position: refs/heads/master@{#61493}