Const overload unexpectedly called in gcc. Compiler bug or compatibility fix?

We have a much larger application that relies on template overloading of char and const char arrays. In gcc 7.5, clang, and visual studio, the code below prints "NON-CONST" for all cases. However, for gcc 8.1 and later, the output is shown below:

#include <iostream>

class MyClass
{
public:
    template <size_t N>
    MyClass(const char (&value)[N])
    {
        std::cout << "CONST "<< value << '\n';
    }

    template <size_t N>
    MyClass(char (&value)[N])
    {
        std::cout << "NON-CONST "<< value << '\n';
    }
};

MyClass test_1()
{
    char buf[30] = "test_1";
    return buf;
}

MyClass test_2()
{
    char buf[30] = "test_2";
    return {buf};
}

void test_3()
{
    char buf[30] = "test_3";
    MyClass x{buf};
}

void test_4()
{
    char buf[30] = "test_4";
    MyClass x(buf);
}

void test_5()
{
    char buf[30] = "test_5";
    MyClass x = buf;
}

int main()
{
    test_1();
    test_2();
    test_3();
    test_4();
    test_5();
}

The gcc 8 and 9 output (from godbolt) is:

CONST test_1
NON-CONST test_2
NON-CONST test_3
NON-CONST test_4
NON-CONST test_5

This appears to me to be a compiler bug, but I guess it could be some other issue related to a language change. Does anybody know definitively?