speedo: Update NSIS helper DLL from Gpg4win
* build-aux/speedo/w32/inst.nsi: Re-enable run-once check. * build-aux/speedo/w32/exdll.c: New. * build-aux/speedo.mk (g4wihelp.dll): Change build commands.
(cherry picked from commit 7359665addda3d47768ed0d64cdb45a65ad2b03d)
- GnuPG-bug-id: T6448