message: Fix docker build to work with https apt sources
diff: @@ -8,10 +8,13 @@ apt-get update
  # for add-apt-repository
  apt-get install -y software-properties-common python-software-properties wget
  +# to allow https apt repositories
  +apt-get install -y apt-transport-https ca-certificates
  +
  # for newer libstdc++
  add-apt-repository -y ppa:ubuntu-toolchain-r/test
  # for clang
  -add-apt-repository 'deb http://apt.llvm.org/precise/ llvm-toolchain-precise-3.8 main'
  +add-apt-repository 'deb https://apt.llvm.org/precise/ llvm-toolchain-precise-3.8 main'
  wget -O - http://apt.llvm.org/llvm-snapshot.gpg.key | apt-key add -
  apt-get update
  