[tests] Fix subobject-linkage error when building with GCC

Placing these tests in anonymous namespaces, is the suggested fix
according to the GCC documentation.

The GCC documentation states: "If a type A depends on a type B with no or
 internal linkage, defining it in multiple translation units would be an
ODR violation because the meaning of B is different in each translation unit.
If A only appears in a single translation unit, the best way to silence the
warning is to give it internal linkage by putting it in an anonymous namespace as well."

Change-Id: I69a1e9b5f1789e9a7a62c762cd499809a72e0ea5
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1836255
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#64128}

test/unittests/compiler/arm64/instruction-selector-arm64-unittest.cc

@@ -372,8 +372,6 @@ const MachInst2 kCanElideChangeUint32ToUint64[] = {
      MachineType::Uint32()},
 };
 
-}  // namespace
-
 
 // -----------------------------------------------------------------------------
 // Logical instructions.
@@ -4955,6 +4953,7 @@ TEST_F(InstructionSelectorTest, PokePairPrepareArgumentsSimd128) {
                expected_poke_pair, expected_poke);
 }
 
+}  // namespace
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8

test/unittests/compiler/common-operator-unittest.cc

@@ -62,8 +62,6 @@ class CommonSharedOperatorTest
     : public TestWithZone,
       public ::testing::WithParamInterface<SharedOperator> {};
 
-}  // namespace
-
 
 TEST_P(CommonSharedOperatorTest, InstancesAreGloballyShared) {
   const SharedOperator& sop = GetParam();
@@ -387,6 +385,7 @@ TEST_F(CommonOperatorTest, Projection) {
   }
 }
 
+}  // namespace
 }  // namespace common_operator_unittest
 }  // namespace compiler
 }  // namespace internal

test/unittests/compiler/js-operator-unittest.cc

@@ -54,9 +54,6 @@ std::ostream& operator<<(std::ostream& os, const SharedOperator& sop) {
   return os << IrOpcode::Mnemonic(sop.opcode);
 }
 
-}  // namespace
-
-
 class JSSharedOperatorTest
     : public TestWithZone,
       public ::testing::WithParamInterface<SharedOperator> {};
@@ -111,6 +108,7 @@ TEST_P(JSSharedOperatorTest, Properties) {
 INSTANTIATE_TEST_SUITE_P(JSOperatorTest, JSSharedOperatorTest,
                          ::testing::ValuesIn(kSharedOperators));
 
+}  // namespace
 }  // namespace js_operator_unittest
 }  // namespace compiler
 }  // namespace internal

test/unittests/compiler/regalloc/register-allocator-unittest.cc

@@ -73,7 +73,6 @@ bool IsParallelMovePresent(int instr_index, Instruction::GapPosition gap_pos,
   return found_match;
 }
 
-}  // namespace
 
 class RegisterAllocatorTest : public InstructionSequenceTest {
  public:
@@ -824,6 +823,7 @@ INSTANTIATE_TEST_SUITE_P(
     ::testing::Combine(::testing::ValuesIn(kParameterTypes),
                        ::testing::Range(0, SlotConstraintTest::kMaxVariant)));
 
+}  // namespace
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8