message: Remove Debian 8 from the build matrix
  Debian 8 ist running CMake 3.0.2, which is ancient at this point. Since
  this release is on "Community LTS" and practically EOL, we should just
  drop it instead of compromising on the CMake version even more (we
  currently ask for 3.2.3).
diff: @@ -28,10 +28,6 @@ config = [
  // Our build matrix. Keys are the operating system labels and values are build configurations.
  buildMatrix: [
  // Various Linux builds for debug and release.
  - ['debian-8', [
  - builds: ['debug', 'release'],
  - tools: ['clang-4'],
  - ]],
  ['centos-6', [
  builds: ['debug', 'release'],
  tools: ['gcc-7'],
  