[D3D12] Ignore `Wnon-virtual-dtor` for the build with Agility SDK

This patch ignores the clang warning `Wnon-virtual-dtor` as a
workaround of the build errors from the `D3D12.h` in the Agility
SDK when building standalone Dawn with Agility SDK.

Bug: 507448270
Change-Id: I6d05c9111883c24f55debf189cd96c0fe309dd55
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/332835
Commit-Queue: Shao, Jiawei <jiawei.shao@intel.com>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>

include/dawn/native/D3D12Backend.h

diff --git a/include/dawn/native/D3D12Backend.h b/include/dawn/native/D3D12Backend.h
index 7ea3f18..1cf65f2 100644
--- a/include/dawn/native/D3D12Backend.h
+++ b/include/dawn/native/D3D12Backend.h
@@ -36,6 +36,7 @@
 #pragma clang diagnostic push
 #pragma clang diagnostic ignored "-Wmicrosoft-enum-value"
 #pragma clang diagnostic ignored "-Wnested-anon-types"
+#pragma clang diagnostic ignored "-Wnon-virtual-dtor"
 #endif
 #include "third_party/agility-sdk/src/build/native/include/d3d12.h"
 #if defined(__clang__)