engine.mk is supposed to be included by engine packages, but it will not
be present in the SDK in the same place as in the main repository.
Move it to include/openssl-engine.mk to avoid this.
Signed-off-by: Eneas U de Queiroz <cotequeiroz@gmail.com>
Co-authored-by: Eneas U de Queiroz <cotequeiroz@gmail.com>
