[rubygems/rubygems] Add Gem::Specification#gem_dir back
If old Bundler versions that unconditionally try to remove this method are run with RubyGems versions without this method, Bundler crashes because it tries to remove a method that does not exist.
We need to wait until RubyGems cannot install any Bundler versions that unconditionally remove this method.
[rubygems/rubygems] Add
Gem::Specification#gem_dirbackIf old Bundler versions that unconditionally try to remove this method
are run with RubyGems versions without this method, Bundler crashes
because it tries to remove a method that does not exist.
We need to wait until RubyGems cannot install any Bundler versions that
unconditionally remove this method.
https://github.com/rubygems/rubygems/commit/98804d261d