Update README.md for installing ponyc on Arch Linux (#2341)
Update README.md for installing ponyc on Arch Linux (#2341)


dipinhora/ponyc,Praetonus/ponyc,CausalityLtd/ponyc,ponylang/ponyc,jemc/ponyc,Praetonus/ponyc,cquinn/ponyc,kulibali/ponyc,kulibali/ponyc,sgebbie/ponyc,Praetonus/ponyc,Theodus/ponyc,sgebbie/ponyc,Theodus/ponyc,cquinn/ponyc,Theodus/ponyc,dipinhora/ponyc,jemc/ponyc,kulibali/ponyc,ponylang/ponyc,sgebbie/ponyc,cquinn/ponyc,sgebbie/ponyc,CausalityLtd/ponyc,sgebbie/ponyc,jemc/ponyc,cquinn/ponyc,Theodus/ponyc,dipinhora/ponyc,Praetonus/ponyc,CausalityLtd/ponyc,ponylang/ponyc,Theodus/ponyc,kulibali/ponyc