[MLton] Cygwin, file open, and reserveEsp

[Stephen Weeks]

> But, I'm guessing that Steve did an strace to find the failing
> system call, so the code up to that point is working.  Can we figure
> out what error is set?

The failing system call is open

	-1 = Posix_FileSys_open (/tmp/package-mlton-cygwin/build/lib/world.mlton, 0x00010601, 0x000001b6)

The resulting errno is EFAULT, and the message is "Bad address".  The
problem is definitely not the string, however, since I have tried
hardwiring in a static string constant and it fails in exactly the
same way.  I have also tried making the same open call earlier in the
processing, and it works fine.  Although, I didn't do a binary search
to find out exactly when things change from good to bad, with self
compiles being so slow and all.

So, the only explanation I have is that we are corrupting the stack,
making a bad C call, or Cygwin is buggy in some other way.