piwicode

Add new symbol directory layout by build-id `/xx/xxxxxxxx.debug`.

3

This protocol is already supported by various tools and lldb. e.g.: https://github.com/llvm-mirror/lldb/blob/d01083a850f577b85501a0902b52fd0930de72c7/source/Symbol/LocateSymbolFile.cpp#L311 Among others it is used by Fuchisa OS builds. This change was unit tested with `fetch_test.go`. It was...

`launch_cvd` selects `--vm_manager=qemu_cli` default for riscv images. It also probes the system and uses `--gpu_mode=drm_virgl` by default. We could add a paragraph about software rendering on host and `--gpu_mode=gfxstream_guest_angle_host_swiftshader` PTAL.