Extract gem files after update

So that test/optparse/test_did_you_mean.rb can find did_you_mean.rb.
2019-11-11 13:10:55 +09:00 · 2019-11-11 13:10:55 +09:00 · 31ee6f6f5d
--- a/common.mk
+++ b/common.mk
@ -1253,6 +1253,7 @@ yes::
 no::

 after-update:: extract-extlibs
+after-update:: extract-gems

 update-remote:: update-src update-download
 update-download:: $(ALWAYS_UPDATE_UNICODE:yes=update-unicode)