EPICS Base compile failure on Windows-x64

[Carl Willis via Tech-talk <tech-talk@aps.anl.gov>]

When attempting to build Epics Base v7.0.2 on Windows 10 using make from msys2 (or other sources) and Visual Studio 2017 Community Edition, this type of error keeps appearing:

cl -EHsc -GR               -nologo -FC -D__STDC__=0 -D_CRT_SECURE_NO_DEPRECATE -D_CRT_NONSTDC_NO_DEPRECATE   -Ox -GL -Oy-   -W3 -w44355 -w44344 -w44251     -D_SILENCE_TR1_NAMESPACE_DEPRECATION_WARNING    -MD -DEPICS_BUILD_DLL -DEPICS_CALL_DLL -TP  -I. -I../O.Common -I. -I../../src/osi/compiler/msvc -I../../src/osi/compiler/default -I. -I../../src/osi/os/WIN32 -I../../src/osi/os/default -I.. -I../../src/as -I../../src/bucketLib -I../../src/calc -I../../src/cvtFast -I../../src/cppStd -I../../src/cxxTemplates -I../../src/dbmf -I../../src/ellLib -I../../src/env -I../../src/error -I../../src/fdmgr -I../../src/flex -I../../src/freeList -I../../src/gpHash -I../../src/iocsh -I../../src/log -I../../src/macLib -I../../src/misc -I../../src/osi -I../../src/pool -I../../src/ring -I../../src/taskwd -I../../src/timer -I../../src/yacc -I../../src/yacc -I../../src/yajl -I/c/epics/base-7.0.2/include/compiler/msvc -I/c/epics/base-7.0.2/include/os/WIN32 -I/c/epics/base-7.0.2/include -I/c/epics/base-7.0.2/include/compiler/msvc -I/c/epics/base-7.0.2/include/os/WIN32 -I/c/epics/base-7.0.2/include        -c ../../src/osi/os/WIN32/epicsTempFile.cpp

epicsTempFile.cpp

c1xx: fatal error C1083: Cannot open source file: '../../src/osi/os/WIN32/epicsTempFile.cpp': No such file or directory

Following the error, I identify the compiler as follows:

C:\epics\base-7.0.2>cl

Microsoft (R) C/C++ Optimizing Compiler Version 19.16.27027.1 for x64

Copyright (C) Microsoft Corporation.  All rights reserved.

My startup script has the following:

rem Set the environment for Microsoft Visual Studio

call "C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Auxiliary\Build\vcvarsall.bat" x64

In other words, the startup script correctly identifies the compiler, but a needed file appears to be missing (??)

Can anyone identify my error or issue?

Thanks

Carl Willis