IMAGE build
LAYER shared/alpine3.8
LAYER shared/alpine3.8-ruby2.4

RUN EOF
    # Install Ruby runtime dependencies
    apk --no-cache add gdbm libressl readline zlib

    # Install Ruby build dependencies
    apk --no-cache add --virtual .deps build-base autoconf gdbm-dev libressl-dev linux-headers readline-dev zlib-dev

    # Download and unpack Ruby
    mkdir -p /usr/src/ruby
    wget http://cache.ruby-lang.org/pub/ruby/2.4/ruby-2.4.5.tar.xz -O - | tar xJf - -C /usr/src/ruby --strip-components=1

    # Compile and install Ruby
    cd /usr/src/ruby
    autoconf
    ./configure --build=x86_64-linux-musl --disable-install-doc --enable-shared
    make -j $(getconf _NPROCESSORS_ONLN)
    make install

    # Install RubyGems and Bundler
    mkdir -p /usr/local/etc
    echo -e 'install: --no-document\nupdate: --no-document' >/usr/local/etc/gemrc
    gem update --system

    # Cleanup
    apk --no-cache del .deps
    cd /root
    rm -r /usr/src/ruby
    rm -rf /root/.gem
EOF