From the “rubygems.rb” file comments:
#
# == RubyGems Defaults, Packaging
#
# RubyGems defaults are stored in rubygems/defaults.rb. If you're packaging
# RubyGems or implementing Ruby you can change RubyGems' defaults.
#
# For RubyGems packagers, provide lib/rubygems/operating_system.rb and
# override any defaults from lib/rubygems/defaults.rb.
#
# For Ruby implementers, provide lib/rubygems/defaults/#{RUBY_ENGINE}.rb and
# override any defaults from lib/rubygems/defaults.rb.
#
# If you need RubyGems to perform extra work on install or uninstall, your
# defaults override file can set pre and post install and uninstall hooks.
# See Gem::pre_install, Gem::pre_uninstall, Gem::post_install,
# Gem::post_uninstall.
#
None of the above has yet been done for SketchUp. Using gems with SketchUp is a new thing, less than 2 years old really.
NOWHERE does Trimble guarantee that gems that need DevKit can be compiled under SketchUp.
What some of us do is re-package gems after compiling, into SketchUp extension packages.