message: chore: package linux binary using Ubuntu 16
  The binary built using Ubuntu 18 requires a higher version of stdlibc++, which
  is not available in Ubuntu 16.
diff: @@ -112,7 +112,7 @@ matrix:
  if: 'tag IS present AND env(GITHUB_TOKEN) IS present'
  language: ruby
  addons: { apt: { packages: [] } }
  - env: REL_PKG=x86_64-unknown-linux-gnu.tar.gz BUILDER_IMAGE=nervos/ckb-docker-builder:bionic-rust-1.34.2
  + env: REL_PKG=x86_64-unknown-linux-gnu.tar.gz BUILDER_IMAGE=nervos/ckb-docker-builder:xenial-rust-1.34.2
  before_install: skip
  before_cache: skip
  cache:
  @@ -120,7 +120,7 @@ matrix:
  - $HOME/.cargo/git
  script:
  - mkdir -p $HOME/.cargo/git
  - - docker run --rm -it -w /ckb -v $(pwd):/ckb -v $HOME/.cargo/git:/root/.cargo/git -e OPENSSL_STATIC=1 -e OPENSSL_LIB_DIR=/usr/lib/x86_64-linux-gnu -e OPENSSL_INCLUDE_DIR=/usr/include/openssl $BUILDER_IMAGE make prod
  + - docker run --rm -it -w /ckb -v $(pwd):/ckb -v $HOME/.cargo/git:/root/.cargo/git -e OPENSSL_STATIC=1 -e OPENSSL_LIB_DIR=/usr/local/lib -e OPENSSL_INCLUDE_DIR=/usr/local/include/openssl $BUILDER_IMAGE make prod
  - openssl aes-256-cbc -K $encrypted_82dff4145bbf_key -iv $encrypted_82dff4145bbf_iv -in devtools/ci/travis-secret.asc.enc -out devtools/ci/travis-secret.asc -d
  - gpg --import devtools/ci/travis-secret.asc
  - devtools/ci/package.sh target/release/ckb
  