Vulkan: Suppress layer warnings about unbound outputs.

This warning could pop up whenever an OpenGL app would write
to a particular output and not bind an attachment. This is
valid in OpenGL. Also it could happen when writing to
gl_FragData instead of gl_FragColor. Since it's hard to fix
every usage we can just suppress the warning.

Also adds a way to change test platform warnings into errors.

Bug: angleproject:2866
Change-Id: I9793f58121ac848d74d6b0131e79ebab2c70f45c
Reviewed-on: https://chromium-review.googlesource.com/c/1462057
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
diff --git a/src/libANGLE/renderer/vulkan/RendererVk.cpp b/src/libANGLE/renderer/vulkan/RendererVk.cpp
index 9ce020a..ec830a7 100644
--- a/src/libANGLE/renderer/vulkan/RendererVk.cpp
+++ b/src/libANGLE/renderer/vulkan/RendererVk.cpp
@@ -103,9 +103,12 @@
 }
 
 // Array of Validation error/warning messages that will be ignored, should include bugID
-constexpr std::array<const char *, 1> kSkippedMessages = {
+constexpr const char *kSkippedMessages[] = {
+    // http://anglebug.com/2866
+    "UNASSIGNED-CoreValidation-Shader-OutputNotConsumed",
     // http://anglebug.com/2796
-    "UNASSIGNED-CoreValidation-Shader-PointSizeMissing"};
+    "UNASSIGNED-CoreValidation-Shader-PointSizeMissing",
+};
 
 // Suppress validation errors that are known
 //  return "true" if given code/prefix/message is known, else return "false"