Missing end padding when including a packed struct #1966.

test/test_suite/struct/struct_pack_error.c3t

@@ -0,0 +1,48 @@
+// #target: macos-x64
+module test;
+import std;
+
+// issue 1966
+
+struct MsgHeader @packed
+{
+    ulong enqueued_by_router_us;
+}
+
+enum ClientState
+{
+    NOT_INITIALIZED,
+    WAITING_FOR_LOGIN,
+    READY,
+    WAITING_FOR_CLOSE,
+}
+
+struct Client
+{
+    ClientState state;
+    MsgHeader header;
+    ushort service_id;
+    ElasticArray(<ulong, 1>) subscribers;
+}
+
+Client[10] clients;
+
+fn void main()
+{
+	void* a = ((void*)(&clients[0])) + Client.sizeof;
+	void* b =  &clients[1];
+}
+
+/* #expect: test.ll
+
+%Client = type <{ i32, %MsgHeader, i16, [2 x i8], %ElasticArray }>
+%MsgHeader = type { i64 }
+%ElasticArray = type { i64, [1 x i64] }
+define void @test.main() #0 {
+entry:
+  %a = alloca ptr, align 8
+  %b = alloca ptr, align 8
+  store ptr getelementptr (i8, ptr @test.clients, i64 32), ptr %a, align 8
+  store ptr getelementptr inbounds (i8, ptr @test.clients, i64 32), ptr %b, align 8
+  ret void
+}