ANDROID: mesa3d: complete Lavapipe build

Follow-up to aosp/3481890, which seemed to work via
"m vulkan.lvp", but was missing:

- a linking step to resolve weak symbols
- GALLIUM_LLVMPIPE + LVP_USE_WSI_PLATFORM cflags

This adds these steps, and requires additional build
rules to fully enable a runnable Lavapipe.

BUG=353540875
TEST=m vulkan.lvp +
     launch_cvd --gpu_mode=gfxstream_guest_angle_host_lavapipe
     boots to UI

Change-Id: Ia678d05de3f02c7a009ac2e017d395ec36de3249