[flang] Fix warnings as errors in ARM build of reduction unit tests.

[mleair]

Summary

Fix warnings as errors in ARM build for the reduction unit tests I recently added.

(see also https://reviews.llvm.org/D107107 and https://reviews.llvm.org/D106820)

[PeteSteinfeld]

All builds, tests, and looks good.

flang/unittests/RuntimeGTest/Reduction.cpp

TEST(Reductions, DoubleMaxMinNorm2) {
   EXPECT_EQ(*loc.ZeroBasedIndexedElement<std::int16_t>(9), 2); // -21
   EXPECT_EQ(*loc.ZeroBasedIndexedElement<std::int16_t>(10), 2); // 22
   EXPECT_EQ(*loc.ZeroBasedIndexedElement<std::int16_t>(11), 2); // 22
   loc.Destroy();
   // Test scalar result for MaxlocDim, MinlocDim, MaxvalDim, MinvalDim.
   // A scalar result occurs when you have a rank 1 array and dim == 1.
   std::vector<int> shape1{24};
   auto array1{MakeArray<TypeCategory::Real, 8>(shape1, rawData)};
-  StaticDescriptor<0, true> statDesc0;
-  Descriptor &scalarResult{statDesc0.descriptor()};
+  StaticDescriptor<1, true> statDesc0[1];
+  Descriptor &scalarResult{statDesc0[0].descriptor()};
   RTNAME(MaxlocDim)
   (scalarResult, *array1, /*KIND=*/2, /*DIM=*/1, __FILE__, __LINE__,
       /*MASK=*/nullptr, /*BACK=*/false);
   EXPECT_EQ(scalarResult.rank(), 0);
   EXPECT_EQ(*scalarResult.ZeroBasedIndexedElement<std::int16_t>(0), 23);
   scalarResult.Destroy();
   RTNAME(MinlocDim)
   (scalarResult, *array1, /*KIND=*/2, /*DIM=*/1, __FILE__, __LINE__,
TEST(Reductions, Logical) {
   EXPECT_EQ(*res.ZeroBasedIndexedElement<std::int32_t>(0), 0);
   EXPECT_EQ(*res.ZeroBasedIndexedElement<std::int32_t>(1), 0);
   res.Destroy();
   // Test scalar result for AllDim.
   // A scalar result occurs when you have a rank 1 array.
   std::vector<int> shape1{4};
   auto array1{MakeArray<TypeCategory::Logical, 4>(
       shape1, std::vector<std::int32_t>{false, false, true, true})};
-  StaticDescriptor<0, true> statDesc0;
-  Descriptor &scalarResult{statDesc0.descriptor()};
+  StaticDescriptor<1, true> statDesc0[1];
+  Descriptor &scalarResult{statDesc0[0].descriptor()};
   RTNAME(AllDim)(scalarResult, *array1, /*DIM=*/1, __FILE__, __LINE__);
   EXPECT_EQ(scalarResult.rank(), 0);
   EXPECT_EQ(*scalarResult.ZeroBasedIndexedElement<std::int32_t>(0), 0);
   scalarResult.Destroy();
   RTNAME(AnyDim)(res, *array, /*DIM=*/1, __FILE__, __LINE__);
   EXPECT_EQ(res.rank(), 1);
   EXPECT_EQ(res.type().raw(), (TypeCode{TypeCategory::Logical, 4}.raw()));
   EXPECT_EQ(res.GetDimension(0).LowerBound(), 1);
TEST(Reductions, FindlocNumeric) {
   res.Destroy();
   // Test scalar result for FindlocDim.
   // A scalar result occurs when you have a rank 1 array, value, and dim == 1.
   std::vector<int> shape1{6};
   auto realArray1{MakeArray<TypeCategory::Real, 8>(shape1,
       std::vector<double>{0.0, -0.0, 1.0, 3.14,
           std::numeric_limits<double>::quiet_NaN(),
           std::numeric_limits<double>::infinity()})};
-  StaticDescriptor<0, true> statDesc0;
-  Descriptor &scalarResult{statDesc0.descriptor()};
+  StaticDescriptor<1, true> statDesc0[1];
+  Descriptor &scalarResult{statDesc0[0].descriptor()};
   RTNAME(FindlocDim)
   (scalarResult, *realArray1, target, 8, /*DIM=*/1, __FILE__, __LINE__, nullptr,
       /*BACK=*/false);
   EXPECT_EQ(scalarResult.rank(), 0);
   EXPECT_EQ(*scalarResult.ZeroBasedIndexedElement<SubscriptValue>(0), 3);
   scalarResult.Destroy();
 }