关于iOS报Could not find ‘minitest‘ (＞= 5.1) among 39 total gem(s)的错误

最近，在运行Flutter项目的时候，执行pod install 命令，报了如下的错误：

/Library/Ruby/Site/2.6.0/rubygems/specification.rb:1413:in `rescue in block in activate_dependencies': Could not find 'minitest' (>= 5.1) among 39 total gem(s) (Gem::MissingSpecError)
Checked in 'GEM_PATH=/Users/myg/.gem/ruby/2.6.0:/System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/gems/2.6.0:/usr/local/Cellar/cocoapods/1.11.3/libexec' at: /usr/local/Cellar/cocoapods/1.11.3/libexec/specifications/activesupport-6.1.5.gemspec, execute `gem env` for more information
    from /Library/Ruby/Site/2.6.0/rubygems/specification.rb:1410:in `block in activate_dependencies'
    from /Library/Ruby/Site/2.6.0/rubygems/specification.rb:1399:in `each'
    from /Library/Ruby/Site/2.6.0/rubygems/specification.rb:1399:in `activate_dependencies'
    from /Library/Ruby/Site/2.6.0/rubygems/specification.rb:1381:in `activate'