WinNT 4.0, 7.1.3, build hangs on "no rule" for libpq.a

Hi folks

I've been trying to build for Windows NT. I have the latest Cygwin
installed, as well as MS Visual Studio 6.0.

When I try to build, the process halts in src\interfaces\libpq. If
I try to manually calle the make command there, I get

$ make
make: *** No rule to make target `libpq.a', needed by `all-lib'. Stop.

Since I noticed the file win32.mak, I tried changing its name to
Makefile and running NMAKE. That was no good either (see below). Has
anyone got an idea how to fix this?

- Brian

C:\Brian\Development\POSTGR~1.3\src\interfaces\libpq>nmake

Microsoft (R) Program Maintenance Utility Version 6.00.8168.0
Copyright (C) Microsoft Corp 1988-1998. All rights reserved.

if not exist ".\Release/" mkdir ".\Release"
cl.exe @C:\TEMP\nma00250.
dllist.c
..\..\include\config.h(677) : fatal error C1083: Cannot open include file:
'os.h': No such file or directory
NMAKE : fatal error U1077: 'cl.exe' : return code '0x2'
Stop.