GPU Metal: report command buffers that failed on the device

DrainStream waited for the submitted command buffers but never looked at
their status, so a kernel that faulted or hung only showed up as missing
output. Print the Metal error of a failed buffer.

Author: ktf

GPU/GPUTracking/Base/metal/GPUReconstructionMetal.mm

@@ -327,6 +327,9 @@ MetalMemRef metalResolve(const GPUReconstructionMetalInternals* internals, const
   // committed, so it never completes. Only what was submitted can be waited for.
   for (id<MTLCommandBuffer> cb : mInternals->submittedBuffers[stream]) {
     [cb waitUntilCompleted];
+    if (cb.status == MTLCommandBufferStatusError) {
+      GPUError("Metal command buffer on stream %d failed: %s", stream, [[cb.error description] UTF8String]);
+    }
     [cb release];
   }
   mInternals->submittedBuffers[stream].clear();