activate_bin_path.rb

redefine_method(gem_class, :activate_bin_path) do |name, *args|
  exec_name = args.first
  return ENV["BUNDLE_BIN_PATH"] if exec_name == "bundle"

  # Copy of Rubygems activate_bin_path impl
  requirement = args.last
  spec = find_spec_for_exe name, exec_name, [requirement]

  gem_bin = File.join(spec.full_gem_path, spec.bindir, exec_name)
  gem_from_path_bin = File.join(File.dirname(spec.loaded_from), spec.bindir, exec_name)
  File.exist?(gem_bin) ? gem_bin : gem_from_path_bin
end