[magma] Use protected memory for depth buffer when necessary

Test: astro:go/magma-tps#L0

Change-Id: I75026e7d19f9715aae46db58e47bef5cd664a92d
diff --git a/lib/magma/third_party/vkcube/cube.cc b/lib/magma/third_party/vkcube/cube.cc
index c30ba94..9af3168 100644
--- a/lib/magma/third_party/vkcube/cube.cc
+++ b/lib/magma/third_party/vkcube/cube.cc
@@ -1033,7 +1033,8 @@
         .samples = VK_SAMPLE_COUNT_1_BIT,
         .tiling = VK_IMAGE_TILING_OPTIMAL,
         .usage = VK_IMAGE_USAGE_DEPTH_STENCIL_ATTACHMENT_BIT,
-        .flags = 0,
+        .flags = demo->protected_output ? VK_IMAGE_CREATE_PROTECTED_BIT
+                                        : static_cast<VkImageCreateFlagBits>(0),
     };
 
     VkImageViewCreateInfo view = {