Add -Wno-delete-non-virtual-dtor to default cxxflags
Add -Wno-delete-non-virtual-dtor to default cxxflags

That warning generates some false negatives that are hard to work
around.

Change-Id: Ib451eca3af7bf2a6bfd24aa966f89496257b9f0d

KhronosGroup/Vulkan-CTS,chadversary/deqp,KhronosGroup/VK-GL-CTS,chadversary/deqp,KhronosGroup/Vulkan-CTS,chadversary/deqp,KhronosGroup/VK-GL-CTS,KhronosGroup/Vulkan-CTS,googlestadia/VK-GL-CTS,KhronosGroup/VK-GL-CTS,chadversary/deqp,chadversary/deqp,KhronosGroup/VK-GL-CTS,googlestadia/VK-GL-CTS,googlestadia/VK-GL-CTS,googlestadia/VK-GL-CTS,KhronosGroup/Vulkan-CTS,googlestadia/VK-GL-CTS,KhronosGroup/VK-GL-CTS,KhronosGroup/Vulkan-CTS,KhronosGroup/Vulkan-CTS,KhronosGroup/VK-GL-CTS,googlestadia/VK-GL-CTS,chadversary/deqp