Disable -ftrivial-auto-var-init= for hot code
Disable -ftrivial-auto-var-init= for hot code

Improves encode_time by 10% on FullStackTest.VP9KSVC_3SL_High and other
tests when -ftrivial-auto-var-init= is used.

vp9_pick_inter_mode can be called recursevely so multiple pred_buf is
neede. So alternative to attribute should be list of bufferes in
ThreadData or TileData.

Bug: 1020220, 977230
Change-Id: I939a468f88c2b5dd2ec235de7564b92bfaa356f5

webmproject/libvpx,ShiftMediaProject/libvpx,ShiftMediaProject/libvpx,webmproject/libvpx,webmproject/libvpx,ShiftMediaProject/libvpx,ShiftMediaProject/libvpx,webmproject/libvpx,webmproject/libvpx,ShiftMediaProject/libvpx,webmproject/libvpx