Avoid reinstalling some Cygwin dependencies on AppVeyor.
Avoid reinstalling some Cygwin dependencies on AppVeyor.

For some reason, OPAM was not happy after we reinstalled curl.

Zimmi48/coq,coq/coq,SkySkimmer/coq,gares/coq,silene/coq,ppedrot/coq,JasonGross/coq,letouzey/coq-wip,gares/coq,Zimmi48/coq,ppedrot/coq,ppedrot/coq,Matafou/coq,maximedenes/coq,SkySkimmer/coq,Zimmi48/coq,letouzey/coq-wip,Matafou/coq,Zimmi48/coq,ejgallego/coq,ppedrot/coq,SkySkimmer/coq,letouzey/coq-wip,gares/coq,maximedenes/coq,coq/coq,gares/coq,letouzey/coq-wip,SkySkimmer/coq,maximedenes/coq,maximedenes/coq,ejgallego/coq,JasonGross/coq,letouzey/coq-wip,Matafou/coq,ejgallego/coq,coq/coq,JasonGross/coq,silene/coq,JasonGross/coq,maximedenes/coq,silene/coq,gares/coq,ppedrot/coq,ejgallego/coq,coq/coq