How to specify non-literal alignment for VS2013?

I'm writing a pool, so its alignment would be type's alignment, which is get from template argument and is not a literal. As C++11's alignas keyword is still not supported by VS2013, I wrote some macro for this:

#define MY_ALIGNOF(x) __builtin_alignof(x)
#define MY_ALN(x) __declspec(align(x))

template<typename T, int BlockSize>
class MyPool
{
    MY_ALN(MY_ALIGNOF(T)) struct MyBlock
    {
        std::int8_t data[sizeof(T) * BlockSize];

        // aligned heap allocators
    };
};

Similar approach works for GCC via __alignof__() and __attribute__((aligned())). However, When I use the above things in VS2013, it claims:

error C2059: syntax error : '__builtin_alignof'

So it seems MSVC alignment specifier don't support using non-literal stuff in declspec? Is there any way to specify alignment via another type's alignment?