[doc] add osx build instructions for homebrew
[doc] add osx build instructions for homebrew

jl777/picocoin,jl777/picocoin,dtebbs/picocoin,dtebbs/picocoin,favioflamingo/picocoin,01BTC10/picocoin,dtebbs/picocoin,mezzovide/picocoin,mezzovide/picocoin,01BTC10/picocoin,jl777/picocoin,favioflamingo/picocoin,mezzovide/picocoin,01BTC10/picocoin