build: Add target to sign the windows installer.
* build-aux/speedo.mk (w32-sign-installer): New. (AUTHENTICODE_KEY): New. (installer-from-source): Use cp instead of mv. Factor code out to ... (MKSWDB_commands): new macro. (sign-installer): New.
Obviously this is more convenient then doing this all by hand.
- Signed-off-by: Werner Koch <wk@gnupg.org>