Add Grafana repository for arm64

Official ARM support as part of the release process of grafana is on
development [0].

For now, the closest official repositories are the ones from fg2it
repository, which is also part of the developers working on the support,
so we are adding it to the sources for now until the official support is
done.

[0] https://github.com/grafana/grafana-docker/issues/117

Bug: #1768585

Signed-off-by: Jorge Niedbalski <jorge.niedbalski@linaro.org>

Change-Id: Iba004f99c0ac92cb660e405c5ac9c61dc7fa81e2

docker/base/Dockerfile.j2

@@ -345,6 +345,7 @@ COPY apt_preferences.{{ base_distro }} /etc/apt/preferences
     ] %}
     {% set remote_apt_keys = [
       'https://people.linaro.org/~marcin.juszkiewicz/debian/stretch/Release.key',
+      'https://bintray.com/user/downloadSubjectPublicKey?username=bintray',
     ] %}
     {% set base_apt_packages = base_apt_packages +
       ['sudo',]

docker/base/sources.list.debian

@@ -12,3 +12,6 @@ deb http://people.linaro.org/~marcin.juszkiewicz/debian/stretch/ ./
 deb http://obs.linaro.org/ERP:/kolla/Debian_9/ ./
 
 deb [arch=amd64] https://packagecloud.io/grafana/stable/debian/ stretch main
+#
+# Unofficial repository for grafana (LP: #1768585).
+deb [arch=arm64] https://dl.bintray.com/fg2it/deb-arm64/ stretch main

docker/grafana/Dockerfile.j2

@@ -5,7 +5,7 @@ LABEL maintainer="{{ maintainer }}" name="{{ image_name }}" build-date="{{ build
 
 {% import "macros.j2" as macros with context %}
 
-{% if base_arch != 'x86_64' %}
+{% if base_arch not in ['aarch64', 'x86_64'] %}
 
 RUN echo 'There are no Grafana external repositories for {{ base_arch }}' \
     && /bin/false