Reduce debug log noise by only logging header msg for
shader debug logs if at least one shader log exists.
diff --git a/MoltenVK/MoltenVK/GPUObjects/MVKQueue.mm b/MoltenVK/MoltenVK/GPUObjects/MVKQueue.mm
index e295b78..e75a85b 100644
--- a/MoltenVK/MoltenVK/GPUObjects/MVKQueue.mm
+++ b/MoltenVK/MoltenVK/GPUObjects/MVKQueue.mm
@@ -358,8 +358,12 @@
 		}
 #if MVK_XCODE_12
 		if (mvkGetMVKConfiguration()->debugMode) {
-			MVKLogInfo("Shader log messages:");
+			bool isFirstMsg = true;
 			for (id<MTLFunctionLog> log in mtlCB.logs) {
+				if (isFirstMsg) {
+					MVKLogInfo("Shader log messages:");
+					isFirstMsg = false;
+				}
 				MVKLogInfo("%s", log.description.UTF8String);
 			}
 		}