IMAGE alpine3.12-ruby2.6_2.6.6-201021
FROM alpine3.12_3.12.1-201021

RUN EOF
    # Install Ruby runtime dependencies
    apk --no-cache add gdbm 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/2.6/ruby-2.6.6.tar.xz -O - | tar xJf - -C /usr/src/ruby --strip-components=1

    # Compile and install Ruby
    cd /usr/src/ruby
    # Hackfix thread stack size
    # https://github.com/docker-library/ruby/issues/196, https://bugs.ruby-lang.org/issues/14387
    wget 'https://bugs.ruby-lang.org/attachments/download/7081/0001-thread_pthread.c-make-get_main_stack-portable-on-lin.patch' -O thread-stack-fix.patch
    patch -p1 -i thread-stack-fix.patch
    autoconf
    # Hackfix isnan/isinf macros
    export ac_cv_func_isnan=yes ac_cv_func_isinf=yes
    ./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