What is RVM Big Sur?

RVM stands for Ruby Version Manager and is a tool used by Ruby developers to switch between different versions of Ruby.

Big Sur is the operating system released by Apple in Nov 2020, notably called macOS 11 for modern Mac computers.

What is the Problem with RVM on Big Sur?

RVM has a problem installing most versions of (noticeably, it will install Ruby 2.7.2 but seems to not install any prior version) on macOS Big Sur released Nov 2020. It will fail with a message like:

Error running '__rvm_make -j12',
please read /Users/name/.rvm/log/1613480016_ruby-3.0.0/make.log
There has been an error while running make. Halting the installation. 

What is the solution to this problem?

On macOS Big Sur, be sure to run this before install a Ruby via RVM:

export warnflags=-Wno-error=implicit-function-declaration

You will want to reference this Github issue for RVM and scroll all the way to the bottom to see this answer.

By Jason