Compilation warning on GCC 11 using -fsanitize=address

[Dologan]

Compiling fmt 9.1.0 with GCC 11 using -fsanitize=address and -Werror=stringop-overflow leads to the following error:

fmt-9.1.0/include/fmt/core.h:2096:48: error: writing 1 byte into a region of size 0 [-Werror=stringop-overflow=]
 2096 |     for (size_t i = 0; i < size; ++i) data_[i] = s[i];

fmt-9.1.0/include/fmt/core.h: In member function 'const Char* fmt::v9::detail::vformat_to(fmt::v9::detail::buffer<T>&, fmt::v9::basic_string_view<Char>, fmt::v9::basic_format_args<fmt::v9::basic_format_context<typename std::conditional<std::is_same<typename fmt::v9::type_identity<T>::type, char>::value, fmt::v9::appender, std::back_insert_iterator<fmt::v9::detail::buffer<typename fmt::v9::type_identity<T>::type> > >::type, typename fmt::v9::type_identity<T>::type> >, fmt::v9::detail::locale_ref)::format_handler::on_format_specs(int, const Char*, const Char*) [with Char = char]':
fmt-9.1.0/include/fmt/core.h:2089:8: note: at offset 4 into destination object 'fmt::v9::detail::fill_t<char>::data_' of size 4
 2089 |   Char data_[max_size] = {Char(' '), Char(0), Char(0), Char(0)};
      |        ^~~~~

This code is apparently currently flagged as being a "Workaround an array initialization issue in gcc 4.8."

[vitaut]

This is a known bug in gcc fixed in trunk but I think we should workaround it considering that many users are affected.

[vitaut]

Worked around in d9bc5f1.