module RakeCompilerDock

def ruby_cc_version(*requirements)


# => "3.4.1:3.3.7:3.2.6"
RakeCompilerDock.ruby_cc_version(Gem::Requirement.new("~> 3.2"))

# => "3.4.1:3.3.7:3.2.6"
RakeCompilerDock.ruby_cc_version("~> 3.2")

# => "3.4.1:2.7.8"
RakeCompilerDock.ruby_cc_version("2.7", "3.4")
For example:

Note that the returned string will contain versions sorted in descending order.

- a Gem::Requirement object
- a String that can be used as a Gem::Requirement constructor argument
- a String that matches the minor version exactly

where each `requirement` may be:
Returns a valid RUBY_CC_VERSION string for the given requirements, 
def ruby_cc_version(*requirements)
  cross = cross_rubies
  output = []
  if requirements.empty?
    output += cross.values
  else
    requirements.each do |requirement|
      if cross[requirement]
        output << cross[requirement]
      else
        requirement = Gem::Requirement.new(requirement) unless requirement.is_a?(Gem::Requirement)
        versions = cross.values.find_all { |v| requirement.satisfied_by?(Gem::Version.new(v)) }
        raise("No matching ruby version for requirement: #{requirement.inspect}") if versions.empty?
        output += versions
      end
    end
  end
  output.uniq.sort.reverse.join(":")
end