Pass down value of `BUNDLE_JOBS` to RubyGems before compiling & introduce a new `gem install -j` flag by Edouard-chin · Pull Request #9171 · ruby/rubygems

Ref #9170 What was the end-user or developer problem that led to this PR? Since #9131, it's possible that Etc.nprocessors returns a value that isn't representative of the number of processo...