[build2] Bug Report: Stack buffer overrun when downgrading a dependency.

[Karen Arutyunov]

Hi Joel,

Thanks for the report.

> Observed:
> 
> Assertion failed: !user_selection () || (keep_out == p.keep_out &&
> config_vars == p.config_vars), file
> E:\tools\build2\build2-toolchain-0.9-a.0\bpkg-0.9.0-a.0.20181119143757.859a34416d0a\bpkg\pkg-build.cxx,
> line 409
> error: process bpkg terminated abnormally: stack buffer overrun

Reproduces for me. I will look into it.

Karen