Gem::Commands::BuildCommand#resolve_gem_name

# File tmp/rubies/ruby-3.3.0/lib/rubygems/commands/build_command.rb, line 115
def resolve_gem_name
  return find_gemspec unless gem_name

  if File.exist?(gem_name)
    gem_name
  else
    find_gemspec("#{gem_name}.gemspec") || find_gemspec(gem_name)
  end
end