Added instructions on setting up uidmap that was missing from podman
setup.

Bug: None
Test: None
Change-Id: I2ba2dacf7f59f285e4377e5f240bb64558459b5e

Recent changes in rust_crates requires rustc 1.60. Also pulls in llvm-14
in the latest debian images.

Bug: 253298221
Tag: #floss
Test: ./floss/build/build-in-podman.py --image-tag floss:latest
Change-Id: Ia2d9a7ada99ada1a13570df00aaf131cf8e3d307

Docker requires root permissions to run and is not preferable for
security reasons. Podman is a drop-in replacement that doesn't run as
root.

Bug: 220203992
Tag: #floss
Test: ./docker-build-image.py --tag floss:latest; ./build-in-docker.py
Change-Id: I813fb63a25bf5588560090ddfb0ad290729a4ff1

Instead of requiring a volume to be created, accept a staging directory
where floss will write all artifacts.

Bug: 224613794
Tag: #floss
Test: ./build-in-docker.py
Change-Id: Id4bb51a070b4649be47de36eaf45f6fac63fea45

After building, always stop the container and clean it up.

Bug: 224613803
Tag: #floss
Test: ./build-in-docker.py
Change-Id: I37b795f05d46a6e0d989acd664733774086eb3b6

Pin the base debian image to a specific sha256 and download the rustup
script to run (avoid calling curl in build script). This will install
the latest Rust stable release (pinned to 1.59.0).

Bug: 220203992
Tag: #floss
Test: docker build
Change-Id: I1b38a6b565e4948be04496233b76008478efeb12

Bug: 223377950
Test: cert/run
Change-Id: I020d9086d0e55f3c17d693194b4ab9f76a8be027

Bug: 220203992
Tag: #floss
Test: None
Change-Id: I1d7432b503c93086a24b438e6e63ccf0a7a92377

Add instructions on how to build with docker and include the dockerfile
used to generate the image used. Also include a python script that can
be run to generate the docker image and build everything.

* `sudo ./docker-build-image.py --tag floss:latest` will build the
  docker image from scratch

* `sudo ./build-in-docker.py` will build Floss in the current
  repository.

Tag: #floss
Bug: 220203992
Test: ./floss/build/docker-build.py and ./build.py inside container
Change-Id: I0888a4e00de2d1f561874d6a555fc847538a131c