don't exclude mac from all builds, just when building on a mac
don't exclude mac from all builds, just when building on a mac

jtbm37/omnisharp-roslyn,nabychan/omnisharp-roslyn,DustinCampbell/omnisharp-roslyn,hal-ler/omnisharp-roslyn,nabychan/omnisharp-roslyn,hal-ler/omnisharp-roslyn,OmniSharp/omnisharp-roslyn,jtbm37/omnisharp-roslyn,OmniSharp/omnisharp-roslyn,DustinCampbell/omnisharp-roslyn