[build2] b v0.8.0 msvc 14.1 - Buffer overrun

[Klaim - Joël Lamotte]

I'm trying to convert GTest to build2, I made a first very simple set
of targets but cannot build or have a report because of this buffer
overrun.
This is on very last Visual Studio up to date compiler. I updated
today, rebuilt build2 v0.8.0 from scratch and reproduced the problem.

I put the code online to easily reproduce it. See below the repro
sequence, followed by what I observe.

A. Joël Lamotte

----------------------------------
# Repro (assuming you built build2 with MSVC 14.1 and in the right
environment + powershell):

git clone https://github.com/Klaim/gtest-build2.git ./gtest-fails
cd gtest-fails
bdep init -C ../build-fails cc

----------------------------------
# What I observe:

PS G:\perso\experiments\gtest-build2> git clone
https://github.com/Klaim/gtest-build2.git ./gtest-fails
Cloning into './gtest-fails'...
remote: Counting objects: 20, done.
remote: Compressing objects: 100% (13/13), done.
remote: Total 20 (delta 4), reused 20 (delta 4), pack-reused 0
Unpacking objects: 100% (20/20), done.
PS G:\perso\experiments\gtest-build2> cd gtest-fails
PS G:\perso\experiments\gtest-build2\gtest-fails> bdep init -C ../build-fails cc
initializing in project G:\perso\experiments\gtest-build2\gtest-fails\
created configuration G:\perso\experiments\gtest-build2\build-fails\ 1
default,forwarded,auto-synchronized
synchronizing:
  new gtest/0.1.0-a.0.20180914142639.7a5e90854bad
error: process b terminated abnormally: stack buffer overrun
PS G:\perso\experiments\gtest-build2\gtest-fails> b --version
build2 0.8.0
libbutl 0.8.0
host x86_64-microsoft-win32-msvc14.1
Copyright (c) 2014-2018 Code Synthesis Ltd
This is free software released under the MIT license.