[flang] Add algorithm include to runtime/file.cpp for std::min

[DavidTruby]

Summary

std::min is only guaranteed to exist in the <algorithm> header.
Currently this builds with libstdc++ because the algorithm include
is coming transitively from elsewhere, however it doesn't build with
libc++.

[sscalpone]

Is this a dup of 1b183918184ecbcd03898badf8d1789ea0f4ffe4?

[DavidTruby]

Yeah, I posted this first but looks like the other got committed first. No problem!

flang/runtime/file.cpp

 //===-- runtime/file.cpp ----------------------------------------*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #include "file.h"
 #include "magic-numbers.h"
 #include "memory.h"
+#include <algorithm>
 #include <cerrno>
 #include <cstring>
 #include <fcntl.h>
 #include <stdlib.h>
 #ifdef _WIN32
 #include <io.h>
 #include <windows.h>
 #else