add documentation on how to verify releases

Author: fstab

HOWTO_VERIFY_RELEASES.md

@@ -0,0 +1,62 @@
+How To Verify Releases
+======================
+
+Releases are built using the `./releases.sh` script, which relies on a couple of Docker images from [hub.docker.com/u/fstab/](https://hub.docker.com/u/fstab/). The Dockerfiles are maintained on [github.com/fstab/docker-grok_exporter-compiler](https://github.com/fstab/docker-grok_exporter-compiler).
+
+In order to run the ARM builds on an AMD64 processor you need `binfmt-support` and `qemu-user-static`, which is enabled by default in Docker for Mac.
+
+After building a release, I do a quick manual test to verify that the binaries work. This file contains some notes on how to manually verify the releases for the different platforms.
+
+linux-arm32v6
+-------------
+
+On a Linux system, follow the instructions from [github.com/dhruvvyas90/qemu-rpi-kernel](https://github.com/dhruvvyas90/qemu-rpi-kernel) to set up an emulated Raspberry PI system:
+
+```bash
+#!/bin/bash
+
+set -e
+
+mkdir ~/qemu_vms
+cd ~/qemu_vms
+sudo apt-get install -y qemu-system-arm
+curl -LO http://downloads.raspberrypi.org/raspbian_lite/images/raspbian_lite-2017-12-01/2017-11-29-raspbian-stretch-lite.zip
+unzip 2017-11-29-raspbian-stretch-lite.zip
+curl -LO https://github.com/dhruvvyas90/qemu-rpi-kernel/raw/master/versatile-pb.dtb
+curl -LO https://github.com/dhruvvyas90/qemu-rpi-kernel/raw/master/kernel-qemu-4.9.59-stretch
+
+cat > run.sh <<EOF
+qemu-system-arm \
+    -kernel kernel-qemu-4.9.59-stretch \
+    -cpu arm1176 \
+    -m 256 \
+    -M versatilepb \
+    -dtb versatile-pb.dtb \
+    -no-reboot \
+    -append "root=/dev/sda2 panic=1 rootfstype=ext4 rw" \
+    -net nic -net user,hostfwd=tcp::5022-:22 \
+    -hda 2017-11-29-raspbian-stretch-lite.img
+EOF
+```
+
+Some info on arm32v6, arm32v7, armhf, armel can be found on the [Raspbian FAQ](https://www.raspbian.org/RaspbianFAQ).
+
+linux-arm64v8
+-------------
+
+Create a Server on [Scaleway](https://cloud.scaleway.com).
+
+linux-amd64
+-----------
+
+Use a plain Ubuntu Docker image.
+
+darwin-amd64
+------------
+
+This is my local development machine.
+
+windows-amd64
+-------------
+
+Set up a VirtualBox VM.