[ruby/rubygems] Update the versions file before fetching infos in parallel

When the compact index client has been released after resolution and is
lazily rebuilt, for example by bundle cache --all-platforms, its first
use happens inside the parallel fetch workers. They then race to create
the client and update the versions file, whose temp file name is based
on the pid, so concurrent renames fail with ENOENT, the fetcher falls
back to an empty index, and caching crashes on an unmaterialized
LazySpecification. Warm the client up on the calling thread instead.

https://github.com/ruby/rubygems/commit/0649eb11ed

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

lib/bundler/fetcher/compact_index.rb

@@ -80,6 +80,12 @@ module Bundler
       end
 
       def fetch_gem_infos(names)
+        # Create the client and update the versions file on this thread.
+        # Otherwise the workers race to lazily create the client and update
+        # the versions file concurrently, e.g. when the client was released
+        # after resolution and is being rebuilt for `bundle cache`.
+        compact_index_client.available?
+
         in_parallel(names) {|name| compact_index_client.info(name) }
       rescue TooManyRequestsError # rubygems.org is rate limiting us, slow down.
         @bundle_worker&.stop