[flang][msvc] Tell windows.h to not define min/max macros.

[Meinersbur]

Summary

Defining macros for min and max breaks using std::min and std::max. Defining NOMINMAX before including the header stops them from being defined.

See https://web.archive.org/web/20170911092732/https://support.microsoft.com/en-us/help/143208/prb-using-stl-in-windows-program-can-cause-min-max-conflicts for details.

This patch is part of the series to make flang compilable with MS Visual Studio.

flang/runtime/file.cpp

 #include "magic-numbers.h"
 #include "memory.h"
 #include <algorithm>
 #include <cerrno>
 #include <cstring>
 #include <fcntl.h>
 #include <stdlib.h>
 #ifdef _WIN32
+#define NOMINMAX
 #include <io.h>
 #include <windows.h>
 #else
 #include <sys/stat.h>
 #include <unistd.h>
 #endif
 
 namespace Fortran::runtime::io {