[UnitTests] Try and pacify gcc-5

This looks like a defect in gcc-5 where it chooses a constexpr
constructor from the initializer-list that it considers to be explicit.

I've tried to reproduce but I can't install anything prior to gcc-6 easily
on my system, and that doesn't have the error. So this is speculative
pacification.

Reported by Steven Wan.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@373820 91177308-0d34-0410-b5e6-96231b3b80d8

unittests/TableGen/AutomataTest.cpp

@@ -62,16 +62,16 @@ TEST(Automata, TupleAutomatonAccepts) {
   Automaton<TupleAutomatonAction> A(makeArrayRef(TupleAutomatonTransitions));
   A.reset();
   EXPECT_TRUE(
-      A.add({SK_a, SK_b, "yeet"}));
+      A.add(TupleAutomatonAction{SK_a, SK_b, "yeet"}));
   A.reset();
   EXPECT_FALSE(
-      A.add({SK_a, SK_a, "yeet"}));
+      A.add(TupleAutomatonAction{SK_a, SK_a, "yeet"}));
   A.reset();
   EXPECT_FALSE(
-      A.add({SK_a, SK_b, "feet"}));
+      A.add(TupleAutomatonAction{SK_a, SK_b, "feet"}));
   A.reset();
   EXPECT_TRUE(
-      A.add({SK_b, SK_b, "foo"}));
+      A.add(TupleAutomatonAction{SK_b, SK_b, "foo"}));
 }
 
 TEST(Automata, NfaAutomatonAccepts) {