assert in vcl 'builder.hxx' line 404 somehow trigger a dialog on windows slaves -> hang

[Norbert Thiebaud]

On Sat, Nov 5, 2016 at 4:20 AM, Norbert Thiebaud <nthiebaud at gmail.com> wrote:
> All the slave bot were hung this morning....
> it turned out that the assert aforementionned was triggering
> and somehow pop-in up a dialog... there was dozen of these stack per box
> the 'mechanism' to cancel hung build was not able to clean these up so
> they stock-piled... messing up further attempt to build.
>

Looks like we need somthing like

_CrtSetReportMode(_CRT_WARN, _CRTDBG_MODE_DEBUG|_CRTDBG_MODE_FILE);
_CrtSetReportFile(_CRT_WARN, _CRTDBG_FILE_STDERR);

which cppuunittester already do, but also for other tests.
iow probably builtin libreoffice when doing automated-ci build