* lib/rubygems: Update to RubyGems master 3de7e0f. Changes:

Only attempt to build extensions for newly-installed gems.  This
  prevents compilation attempts at gem activation time for gems that
  already have extensions built.

  Fix crash in the dependency resolver for dependencies that cannot be
  resolved.

* test/rubygems:  ditto.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@43368 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

lib/rubygems/dependency_resolver/vendor_set.rb

@@ -28,6 +28,9 @@ class Gem::DependencyResolver::VendorSet
 
     spec = Gem::Specification.load gemspec
 
+    raise Gem::GemNotFoundException,
+          "unable to find #{gemspec} for gem #{name}" unless spec
+
     key = "#{spec.name}-#{spec.version}-#{spec.platform}"
 
     @specs[key] = spec