cipher: Fix ElGamal decryption.
* cipher/elgamal.c (elg_decrypt): Call sexp_build always. * cipher/rsa.c (rsa_decrypt): Return an error code of sexp_build when RC != 0.
Cherry-pick master commit of:
6d1d50ba3aad1850975f717adbedb4cb8b236fa7
- Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>