Auto merge of #6645 - bundler:colby/require-etc, r=colby-swandale

require `etc` in Bundler#user_home

### What was the end-user problem that led to this PR?

In some cases, we are sending messages to the`Etc` library which may not be loaded.

### What was your diagnosis of the problem?

See #6640

### What is your fix for the problem, implemented in this PR?

Require the `etc` library before we use it

Fixes #6640

(cherry picked from commit 5dcfc31)

lib/bundler.rb

@@ -170,6 +170,7 @@ def user_home
         end
 
         if warning
+          Kernel.send(:require, "etc")
           user_home = tmp_home_path(Etc.getlogin, warning)
           Bundler.ui.warn "#{warning}\nBundler will use `#{user_home}' as your home directory temporarily.\n"
           user_home