Windows builders will need a cygwin gcc now

[Stephan Bergmann]

On 11/21/2017 10:21 PM, Thorsten Behrens wrote:
> with the imminent merge of
> https://gerrit.libreoffice.org/#/q/topic:gpg4libre-win32 into master
> (and hopefully in time for 6.0), Windows builders will need a minimal
> version of gcc, to satisfy gpgme's windres requirement.

With 
<https://cgit.freedesktop.org/libreoffice/core/commit/?id=e0d94237878d4949573fc9b6d97eea3146cada6d> 
"Use Executable_cpp instead of default gcc as preprocessor for windres" 
that requirement should be moot again.