claws-mail: Add missing libgcrypt dependency

* otherwise fails with:
  | claws-mail/3.9.0-r0/claws-mail-3.9.0/src/common/ssl.c:35:20:
    fatal error: gcrypt.h: No such file or directory
  |  #include <gcrypt.h>

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>