Fix FreeBSD build instructions (#3526)
Fix FreeBSD build instructions (#3526)

We require GNU Make.
ponylang/ponyc,jemc/ponyc,jemc/ponyc,sgebbie/ponyc,sgebbie/ponyc,ponylang/ponyc,sgebbie/ponyc,jemc/ponyc,dipinhora/ponyc,sgebbie/ponyc,dipinhora/ponyc,sgebbie/ponyc,ponylang/ponyc,dipinhora/ponyc