RUBY_CFLAGS="-w" asdf install ruby 2.6.3
# Note: Some gems may fail to install during `bundle install`, such as `pg`.
# Follow the prompts to install them one-by-one.
Solution originally sourced from here: rbenv/ruby-build#1691 (comment)
- Lanny Bose on an M1 MacBook Air on MacOS 12.1