Fix libgui warnings

The warnings were being hidden by the use of -isystem to include
frameworks/native/include.

Bug: 31752268
Test: m -j
Change-Id: Idba8278bc0a73886ecb7978617854b433c0b5875
diff --git a/include/gui/IGraphicBufferProducer.h b/include/gui/IGraphicBufferProducer.h
index 8775383..982cc9d 100644
--- a/include/gui/IGraphicBufferProducer.h
+++ b/include/gui/IGraphicBufferProducer.h
@@ -352,7 +352,7 @@
     };
 
     // QueueBufferOutput must be a POD structure
-    struct __attribute__ ((__packed__)) QueueBufferOutput {
+    struct QueueBufferOutput {
         // outWidth - filled with default width applied to the buffer
         // outHeight - filled with default height applied to the buffer
         // outTransformHint - filled with default transform applied to the buffer