Include prerelease gems in compact index during incremental update

In `update_index`, the call to `update_compact_index` only received
`released` specs, excluding prerelease gems from the compact index
files (`versions`, `info/<gemname>`). Since modern Bundler prefers the
compact index, prerelease gems were effectively invisible after an
incremental `--update`.

Fix by passing all specs (both released and prerelease) to
`update_compact_index`.

Fixes #48

Author: sudoremo

lib/rubygems/indexer.rb

@@ -450,7 +450,7 @@ def update_index
 
     if @build_compact
       Gem.time "Updated compact index files" do
-        files += update_compact_index released, @dest_directory, @directory
+        files += update_compact_index specs, @dest_directory, @directory
       end
     end
 

test/rubygems/test_gem_indexer.rb

@@ -462,11 +462,12 @@ def test_update_index
       assert_equal <<~INFO_FILE, File.read(File.join(infodir, "d"))
         #{info_d_file.chomp}
         2.1 |checksum:#{file_sha256(File.join(gems, "d-2.1.gem"))}
+        2.2.a |checksum:#{file_sha256(File.join(gems, "d-2.2.a.gem"))}
       INFO_FILE
 
       assert_equal <<~VERSIONS_FILE, File.read(File.join(@indexerdir, "versions"))
         #{versions_file.chomp}
-        d 2.1 #{file_md5(File.join(@indexerdir, "info", "d"))}
+        d 2.1,2.2.a #{file_md5(File.join(@indexerdir, "info", "d"))}
         e 1 #{file_md5(File.join(@indexerdir, "info", "e"))}
       VERSIONS_FILE