Should this be a constexpr or not?

Consider this code snippet (godbolt):

#include <cstdio>
#include <string>
#include <string_view>

struct Option
{
    std::string_view name;

    constexpr Option( std::string_view const n ) noexcept : name{n} {}
};

template< std::size_t N >
class TransformedOption : public Option
{
public:
    constexpr TransformedOption( std::string_view const nameStr ) :
        Option{ { nameStorage_, N - 1 } }
    {
        for ( auto i = 0U; i < N; ++i )
        {
            if ( nameStr[ i ] == '_' ) { nameStorage_[ i ] = '-'; }
            else                       { nameStorage_[ i ] = nameStr[ i ]; }
        }
    }
    private:
        char nameStorage_[ N ] = {};
};

template< std::size_t N >
constexpr TransformedOption< N > make( char const (&nameStr)[ N ] ) noexcept
{
    return TransformedOption< N  >{ nameStr };
}

int main()
{
    /*constexpr*/ auto t = make( "abcd_efgh_ijkl_mnop_peqst" );
    std::printf( "%s\n", t.name.data() );
    return 0;
}

Basically, I want to perform compile-time string transformation by replacing each _ with - and making sure that the final binary contains only the transformed string (not the original).

I've tried Clang 10.0.1, GCC 10.2 and MSVC 19.24 (see above godbolt link). The weird stuff the following:

• if constexpr is commented-out in main, then MSVC generates incorrect code (i.e. runtime transformation of string), but both GCC and clang generate correct code (i.e. transformed string constant is embedded into the assembly)
• if constexpr is not commented-out in main, then MSVC generates correct code (i.e. transformed string constant is embedded into the assembly), but both GCC and clang fail to compile the code, stating that t is not initialized by constant expression (see godbolt). The weirdest thing is the GCC error message, which outputs the transformed string in its error and states that it's not a constant expression.

Well, which compiler is right, according to the C++ standard? To whom should I report a bug? To GCC and Clang folks or to Microsoft?