meson: Add MSVC narrowing-int-to-char warnings

MSVC seems quite keen to warn us that we're narrowing an int into a
char, even if it fits entirely within range.

Signed-off-by: Daniel Stone <daniels@collabora.com>
Reviewed-by: Erik Faye-Lund <erik.faye-lund@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6227>
1 file changed