meson: Fix Clang microsoft-enum-value detection.

Fixes: 3aee462781a ("meson: add windows compiler checks and libraries")
Signed-off-by: Vinson Lee <vlee@freedesktop.org>
Reviewed-by: Dylan Baker <dylan@pnwbakers.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7543>
(cherry picked from commit bb46a010bbe9f703ff9d48e450dbd6529906b8e9)
2 files changed