meta-speech-framework: enable building Alexa voiceagent against zeus

meta-speech-framework: enable building Alexa voiceagent against zeus

Changes:
- Tweak LAYERSERIES_COMPAT variable for alexa-auto-sdk's meta-aac
  layer to append zeus, since it's unclear when Amazon will get around
  to a new release that adds zeus support and it's straightforward to
  get it to build against zeus.
- Add BBMASK for nghttp2 recipe in meta-aac to avoid overlaying the
  one for the same version now available in meta-networking. This
  avoids rebuilding a bunch of dependencies when reconfiguring to
  enable agl-voiceagent-alexa.
- Add bbappend for avs-device-sdk to add a patch to disable -Werror
  for new g++ 9 "deprecated-copy" warning in the packaged copy of
  googletest, which avoids a build failure.

Bug-AGL: SPEC-2932

Change-Id: I469d07bafd8a4faf625191eb553ab7f762efb480
Signed-off-by: Scott Murray <scott.murray@konsulko.com>