Add Apple silicon support

[msonderegger]

Installation currently doesn't work on OS X with Apple Silicon processor, which is now the default on most new Apple machines.

My system info:

The issue has to do with the Homebrew steps in pgdb, because Homebrew works differently by default on Macs with Intel processors (old default) and M1 / Apple Silicon (new default). See here : "Homebrew installs files into the /opt/homebrew/ folder".

I got installation to work by making these changes in pgdb :

But pgdb should probably do this automatically:

• check if this is an Apple Silicon processor
• if so, change how influxdb is installed

[msonderegger]

@michaelhaaf ?

[michaelhaaf]

I should be able to incorporate this into #167 pretty easily once that's finished