If you are runnig into issues installing RVM and Ruby on macOS Big Sur and you get the following “error running ‘__rvm_make -j4′”. Here is a solution to get Ruby installed under RVM.
brew install homebrew/portable-ruby/portable-openssl rvm reinstall ruby-2.3.1 --with-openssl-dir=/usr/local/opt/portable-openssl/
I have not spent time diving into the root cause of the error, just glad someone had a solution to the problem. Here is the original Github issue report that had a solution that worked: https://github.com/rvm/rvm/issues/4484.