cppgc: stack unittest: Fix order of attributes

gcc complains about the 'extern "C"' going after attributes.

Bug: v8:11710
Change-Id: If253c73bdfb2473267511d556950da37b80f790b
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2877797Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Anton Bikineev <bikineev@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74426}

test/unittests/heap/cppgc/stack-unittest.cc

@@ -276,20 +276,20 @@ namespace {
 // to make sure that:
 // 1) there is no .plt indirection (i.e. visibility is hidden);
 // 2) stack is realigned in the function prologue.
-V8_NOINLINE
+extern "C" V8_NOINLINE
 #if defined(__clang__)
-__attribute__((used))
+    __attribute__((used))
 #if !defined(V8_OS_WIN)
-__attribute__((visibility("hidden")))
+    __attribute__((visibility("hidden")))
 #endif  // !defined(V8_OS_WIN)
 #ifdef __has_attribute
 #if __has_attribute(force_align_arg_pointer)
-__attribute__((force_align_arg_pointer))
+    __attribute__((force_align_arg_pointer))
 #endif  // __has_attribute(force_align_arg_pointer)
 #endif  //  __has_attribute
 #endif  // defined(__clang__)
-extern "C" void
-IteratePointersNoMangling(Stack* stack, StackVisitor* visitor) {
+    void
+    IteratePointersNoMangling(Stack* stack, StackVisitor* visitor) {
   stack->IteratePointers(visitor);
 }
 }  // namespace