Install the core/openssl-1.0 and aur/gcc5 packages
curl -fsSL https://gist.github.com/mislav/055441129184a1512bb5.txt > ruby2.x-openssl.patch
CC=gcc-5 PKG_CONFIG_PATH=/usr/lib/openssl-1.0/pkgconfig:/usr/lib/pkgconfig RUBY_EXTRA_CONFIGURE_OPTIONS="--with-openssl-dir=/usr/lib/openssl-1.0" RUBY_APPLY_PATCHES=~/ruby2.x-openssl.patch asdf install ruby 2.0.0-p648