How do I determine the native endian at compile time?

At runtime, you can determine if the native endian is a little endian, for example:

#include<iostream>

const int bomb = 1;
bool is_little_endian(){
    return*reinterpret_cast<const char*>(&bom)==1;
}

int main()
{
    const pool b=is_little_endian();
    std::cout<<b<<'\n';
}

C++11 added a constant expression function (constexpr), so I thought that if I changed const to constexpr, I could make a decision at the time of compilation, but reinterpret_cast doesn't seem to work in constant expressions, resulting in a compilation error.

#include<iostream>

constexprint bomb = 1;
constexprbool is_little_endian(){
    return*reinterpret_cast<const char*>(&bom)==1;
}

int main()
{
    constexpr bool b=is_little_endian();
    std::cout<<b<<'\n';
}

;

#clang++-Wall-std=c++11 test_endian.cpp
test_endian.cpp:4:16:error:constexpr function never produce a constant
      expression [-Winvalid-constexpr]
constexprbool is_little_endian(){
               ^
test_endian.cpp:5:10:note:reinterpret_cast is not allowed in a constant
      expression
        return*reinterpret_cast<const char*>(&bom)==1;
                ^
1 error generated.

I think the native endian has been decided at the time of compilation, so I would like to make a decision at the time of compilation, but is there any other way besides using the compiler's own macro like Boost library?

リトルIt would be best if you could categorize it into Little Endian/Big Endian/Other, not just Little Endian or not.

■Additional
The purpose is to optimize the implementation of external data endian-native endian relationships when creating functions/classes that convert external and internal data.