travis: install Ceph development packages for go-ceph

The Ceph community does not guarantee that arm64 packages get build and
published with each release. In order to prevent falling back to ancient
Ceph versions from ubuntu-ports, add an unsigned repository with Ceph
Nautilus 14.2.5.

Signed-off-by: Niels de Vos <ndevos@redhat.com>

.travis.yml

@@ -36,6 +36,19 @@ before_install:
   - curl
     https://raw.githubusercontent.com/golang/dep/${DEP_VERSION}/install.sh|sh
 
+before_script:
+  - curl https://download.ceph.com/keys/release.asc | sudo apt-key add -
+  - sudo apt-add-repository
+    "deb https://download.ceph.com/debian-nautilus xenial main"
+  # Ceph does not guarantee arm64 builds, fallback to ceph 14.2.5
+  # yamllint disable rule:line-length
+  - test "$(arch)" != "aarch64" || sudo apt-add-repository
+    "deb https://chacra.ceph.com/r/ceph/nautilus/af06652dc9b2da8c6aadbbecdfafdc7e235abe7d/ubuntu/xenial/flavors/default/ xenial main"
+  # yamllint enable rule:line-length
+  - sudo apt-get -qq update
+  # only the arm64 fallback repo is unsigned and needs --allow-unauthenticated
+  - sudo apt-get -y --allow-unauthenticated install librados-dev librbd-dev
+
 jobs:
   include:
     - name: static-check-make