Disable trivial pair copy/move tests when unsupported

[dim]

Summary

On FreeBSD, for ABI compatibility reasons, the pair trivial copy
constructor is disabled, using the aptly-named
_LIBCPP_DEPRECATED_ABI_DISABLE_PAIR_TRIVIAL_COPY_CTOR define.

Disable the related tests when this define is on, so they don't fail
unexpectedly.

test/std/utilities/utility/pairs/pairs.pair/trivial_copy_move.pass.cpp

struct Dummy {
   Dummy(Dummy &&) = default;
 };
 
 int main()
 {
     typedef std::pair<int, short> P;
     {
         static_assert(std::is_copy_constructible<P>::value, "");
+#if !defined(_LIBCPP_DEPRECATED_ABI_DISABLE_PAIR_TRIVIAL_COPY_CTOR)
         static_assert(std::is_trivially_copy_constructible<P>::value, "");
+#endif
     }
 #if TEST_STD_VER >= 11
     {
         static_assert(std::is_move_constructible<P>::value, "");
+#if !defined(_LIBCPP_DEPRECATED_ABI_DISABLE_PAIR_TRIVIAL_COPY_CTOR)
         static_assert(std::is_trivially_move_constructible<P>::value, "");
+#endif
     }
     {
         using P1 = std::pair<Dummy, int>;
         static_assert(!std::is_copy_constructible<P1>::value, "");
         static_assert(!std::is_trivially_copy_constructible<P1>::value, "");
         static_assert(std::is_move_constructible<P1>::value, "");
+#if !defined(_LIBCPP_DEPRECATED_ABI_DISABLE_PAIR_TRIVIAL_COPY_CTOR)
         static_assert(std::is_trivially_move_constructible<P1>::value, "");
+#endif
     }
 #endif
 }