Detect Cygwin environment on Windows
Detect Cygwin environment on Windows

Currently if Servo is built using Cygwin, it is incorrectly classified
as "unknown" host, which makes downloading Rust and Cargo fail. This
commit fixes that.

sadmansk/servo,jimberlage/servo,szeged/servo,avadacatavra/servo,SimonSapin/servo,nnethercote/servo,canaltinova/servo,nrc/servo,KiChjang/servo,larsbergstrom/servo,splav/servo,mbrubeck/servo,emilio/servo,rnestler/servo,dati91/servo,avadacatavra/servo,anthgur/servo,cbrewster/servo,pyfisch/servo,jimberlage/servo,dsandeephegde/servo,splav/servo,dati91/servo,dati91/servo,thiagopnts/servo,emilio/servo,KiChjang/servo,fiji-flo/servo,rnestler/servo,CJ8664/servo,saneyuki/servo,SimonSapin/servo,canaltinova/servo,pyfisch/servo,mattnenterprise/servo,nnethercote/servo,mbrubeck/servo,notriddle/servo,cbrewster/servo,paulrouget/servo,SimonSapin/servo,ConnorGBrewster/servo,peterjoel/servo,fiji-flo/servo,peterjoel/servo,pyfisch/servo,KiChjang/servo,saneyuki/servo,larsbergstrom/servo,mattnenterprise/servo,peterjoel/servo,mattnenterprise/servo,upsuper/servo,peterjoel/servo,avadacatavra/servo,larsbergstrom/servo,avadacatavra/servo,splav/servo,notriddle/servo,CJ8664/servo,upsuper/servo,CJ8664/servo,sadmansk/servo,avadacatavra/servo,avadacatavra/servo,peterjoel/servo,mattnenterprise/servo,notriddle/servo,pyfisch/servo,larsbergstrom/servo,larsbergstrom/servo,emilio/servo,anthgur/servo,mbrubeck/servo,eddyb/servo,steveklabnik/servo,paulrouget/servo,DominoTree/servo,paulrouget/servo,notriddle/servo,larsbergstrom/servo,eddyb/servo,ConnorGBrewster/servo,splav/servo,mattnenterprise/servo,mbrubeck/servo,pyfisch/servo,saneyuki/servo,dsandeephegde/servo,DominoTree/servo,mbrubeck/servo,fiji-flo/servo,szeged/servo,larsbergstrom/servo,peterjoel/servo,canaltinova/servo,paulrouget/servo,dsandeephegde/servo,DominoTree/servo,rnestler/servo,notriddle/servo,peterjoel/servo,pyfisch/servo,cbrewster/servo,splav/servo,peterjoel/servo,cbrewster/servo,DominoTree/servo,canaltinova/servo,SimonSapin/servo,avadacatavra/servo,thiagopnts/servo,thiagopnts/servo,canaltinova/servo,sadmansk/servo,DominoTree/servo,KiChjang/servo,cbrewster/servo,CJ8664/servo,dati91/servo,KiChjang/servo,mbrubeck/servo,CJ8664/servo,SimonSapin/servo,dati91/servo,pyfisch/servo,szeged/servo,nnethercote/servo,larsbergstrom/servo,canaltinova/servo,upsuper/servo,avadacatavra/servo,KiChjang/servo,paulrouget/servo,nnethercote/servo,KiChjang/servo,upsuper/servo,rnestler/servo,ConnorGBrewster/servo,DominoTree/servo,anthgur/servo,fiji-flo/servo,cbrewster/servo,szeged/servo,thiagopnts/servo,anthgur/servo,DominoTree/servo,jimberlage/servo,cbrewster/servo,nnethercote/servo,DominoTree/servo,dsandeephegde/servo,jimberlage/servo,nnethercote/servo,SimonSapin/servo,upsuper/servo,notriddle/servo,paulrouget/servo,szeged/servo,nnethercote/servo,CJ8664/servo,nrc/servo,dsandeephegde/servo,nnethercote/servo,ConnorGBrewster/servo,saneyuki/servo,jimberlage/servo,larsbergstrom/servo,steveklabnik/servo,cbrewster/servo,thiagopnts/servo,rnestler/servo,dati91/servo,mattnenterprise/servo,splav/servo,dati91/servo,canaltinova/servo,fiji-flo/servo,splav/servo,eddyb/servo,thiagopnts/servo,peterjoel/servo,rnestler/servo,saneyuki/servo,sadmansk/servo,paulrouget/servo,splav/servo,thiagopnts/servo,emilio/servo,emilio/servo,sadmansk/servo,sadmansk/servo,nrc/servo,szeged/servo,saneyuki/servo,canaltinova/servo,pyfisch/servo,eddyb/servo,CJ8664/servo,anthgur/servo,jimberlage/servo,saneyuki/servo,eddyb/servo,KiChjang/servo,anthgur/servo,DominoTree/servo,mattnenterprise/servo,dsandeephegde/servo,steveklabnik/servo,szeged/servo,anthgur/servo,emilio/servo,jimberlage/servo,paulrouget/servo,pyfisch/servo,saneyuki/servo,notriddle/servo,emilio/servo,thiagopnts/servo,upsuper/servo,szeged/servo,nnethercote/servo,saneyuki/servo,nrc/servo,ConnorGBrewster/servo,notriddle/servo,ConnorGBrewster/servo,anthgur/servo,larsbergstrom/servo,nnethercote/servo,nrc/servo,eddyb/servo,nrc/servo,fiji-flo/servo,emilio/servo,emilio/servo,mattnenterprise/servo,splav/servo,sadmansk/servo,ConnorGBrewster/servo,jimberlage/servo,CJ8664/servo,paulrouget/servo,fiji-flo/servo,mbrubeck/servo,upsuper/servo,steveklabnik/servo,sadmansk/servo,dsandeephegde/servo,paulrouget/servo,szeged/servo,emilio/servo,peterjoel/servo,DominoTree/servo,notriddle/servo,KiChjang/servo,SimonSapin/servo,pyfisch/servo,ConnorGBrewster/servo,saneyuki/servo,KiChjang/servo,mbrubeck/servo,notriddle/servo,rnestler/servo,szeged/servo,rnestler/servo,steveklabnik/servo,jimberlage/servo,splav/servo,fiji-flo/servo,nrc/servo,SimonSapin/servo,dsandeephegde/servo,steveklabnik/servo,eddyb/servo,steveklabnik/servo,dati91/servo,upsuper/servo,eddyb/servo