[flang] Add missing include for std::min

This was causing the build to fail on macos.

Differential Revision: https://reviews.llvm.org/D83237

Author: tskeith

flang/runtime/file.cpp

@@ -9,6 +9,7 @@
 #include "file.h"
 #include "magic-numbers.h"
 #include "memory.h"
+#include <algorithm>
 #include <cerrno>
 #include <cstring>
 #include <fcntl.h>