So Ruby 2.7 was released at Xmas'19 and I got some errors when compiling it in Linux Mint 19.1. Some libraries were not configured. The errors ocurred at the linking phase of make. Five libraries got errors, and I'll walk across their solutions:

• openssl:
  sudo apt install libssl-dev
• gdbm:
  sudo apt install libgdbm-dev
• dbm:
  sudo apt install libqdbm-dev
• readline:
  sudo apt install libedit-dev
• zlib:
  sudo apt install libz-dev
cd /lib/x86_64-linux-gnu/
sudo ln -s libz.so.1 liblibz.so

Enjoy!

The apt-get way don't install the latest stable Ruby (2.1.1), even on Ubuntu 14.04. Instead, I got 1.9.3 that way. RVM can be easy, but to work with Apache I'd need a system-wide installation independent of the RVM environment. So I've decided to install Ruby from source. I had problems around readline, but after seeing this hint, the solution that worked for me is:

./configure --with-readline-dir=/usr/lib/x86_64-linux-gnu/libreadline.so
make
make install

on the directory of the unpacked source of Ruby 2.1.1, as root. I suspect there is a more elegant solution out there, but this is enough for me at this time.