ruby/rubygems bundler-v2.3.6 on GitHub

Enhancements:

Use Gem::Platform.local instead of RUBY_PLATFORM when displaying local platform #5306
Lock standard.yml to the required ruby version #5284
Use Fiddle in bundle doctor to check for dynamic library presence #5173

Fix edge case where gems were incorrectly removed from the lockfile #5302
Fix force_ruby_platform ignored when lockfile includes current specific platform #5304
Create minitest file to underscored path in "bundle gem" command with dashed gem name #5273
Fix regression with old marshaled specs having null required_rubygems_version #5291