Compiling with DOCTEST_CONFIG_COLORS_ANSI fails on Windows

[psfrolov]

Description

The following code fails on Windows with MSVC because STDOUT_FILENO is not defined.

#define DOCTEST_CONFIG_COLORS_ANSI
#define DOCTEST_CONFIG_IMPLEMENT_WITH_MAIN
#include <doctest/doctest.h>

Workaround

#ifdef _WIN32
#include <cstdio>
const int STDOUT_FILENO{fileno(stdout)};
#endif

#define DOCTEST_CONFIG_COLORS_ANSI
#define DOCTEST_CONFIG_IMPLEMENT_WITH_MAIN
#include <doctest/doctest.h>

Fix

Replace STDOUT_FILENO with fileno(stdout) in doctest. This should work across platforms.