chore: docker fixes, including clean bootstrap

[edwintorok]

The docker-podman wrapper created volume mounts are owned by the root
user inside the container, and the doom user wouldn't have write access.
Need to specify --user-ns=keep-id flag to map $UID from the host to $UID
from the container without using subuids: that way user inside container
can modify.

SELinux is on by default on Fedora36, thus volume mounts need to specify
the 'Z' flag to relabel the directory being mounted.

I've only tested this on Fedora, applies on top of #371.
Opened as a separate PR since it might need testing on other OSes, to check that the docker command still works there, in particular on non-SELinux systems.

[connorgmeehan]

Hi @edwintorok, testing this on macos I get the following error. It seems to work if I set --user-ns=auto.

I guess we'll need to detect if the user is using the podman-docker wrapper or just vanilla docker. Do you have any ideas on the best way to do this?

1. Setting up branch
 - Success!  Checked out doom-nvim-contrib branch at:
   /Users/connormeehan/.config/nvim/tools/doom-nvim-contrib

2. Setting up docker environment
 - Docker image does not exist.  Building docker image...
[+] Building 3.5s (18/18) FINISHED
 => [internal] load build definition from Dockerfile                                                                                                                                                                                     0.0s
 => => transferring dockerfile: 37B                                                                                                                                                                                                      0.0s
 => [internal] load .dockerignore                                                                                                                                                                                                        0.0s
 => => transferring context: 2B                                                                                                                                                                                                          0.0s
 => [internal] load metadata for docker.io/library/archlinux:latest                                                                                                                                                                      3.4s
 => [auth] library/archlinux:pull token for registry-1.docker.io                                                                                                                                                                         0.0s
 => [ 1/12] FROM docker.io/library/archlinux:latest@sha256:3a527a8a777472e60c23cf7a610b4d082913a786254c002d1cafdcec7f6129d9                                                                                                              0.0s
 => [internal] load build context                                                                                                                                                                                                        0.0s
 => => transferring context: 38B                                                                                                                                                                                                         0.0s
 => CACHED [ 2/12] RUN PACMAN -Syy                                                                                                                                                                                                       0.0s
 => CACHED [ 3/12] RUN pacman -Sy neovim --noconfirm                                                                                                                                                                                     0.0s
 => CACHED [ 4/12] RUN pacman -Sy ripgrep nodejs-lts-fermium npm git bash gcc jq --noconfirm                                                                                                                                             0.0s
 => CACHED [ 5/12] RUN pacman -Sy wget unzip --noconfirm                                                                                                                                                                                 0.0s
 => CACHED [ 6/12] RUN npm i -g chokidar-cli                                                                                                                                                                                             0.0s
 => CACHED [ 7/12] RUN groupadd doom                                                                                                                                                                                                     0.0s
 => CACHED [ 8/12] RUN useradd -m -g doom doom                                                                                                                                                                                           0.0s
 => CACHED [ 9/12] RUN mkdir /usr/local/lib/node_modules                                                                                                                                                                                 0.0s
 => CACHED [10/12] RUN chown -R doom:doom /usr/local/lib/node_modules/                                                                                                                                                                   0.0s
 => CACHED [11/12] WORKDIR /home/doom                                                                                                                                                                                                    0.0s
 => CACHED [12/12] COPY _docker_entry.sh /usr/local/bin/                                                                                                                                                                                 0.0s
 => exporting to image                                                                                                                                                                                                                   0.0s
 => => exporting layers                                                                                                                                                                                                                  0.0s
 => => writing image sha256:2dd0faf2e2abfbe793e983bb8f7289a7e88378b4b939e2af4c596cf62d3ce967                                                                                                                                             0.0s
 => => naming to docker.io/library/doom-nvim-contrib                                                                                                                                                                                     0.0s

Use 'docker scan' to run Snyk tests against images to find vulnerabilities and learn how to fix them
 - Success! Running docker container doom-nvim-contrib-container...

docker: --userns: invalid USER mode.
See 'docker run --help'.

[edwintorok]

Thanks for testing, should be possible to detect podman with $(command -v docker podman | head -n1) and then changing flags accordingly.
I'll do some experiments on Ubuntu (which doesn't have SELinux) and try to update this PR with a script that works on both Ubuntu and Fedora (probably later today/tomorrow).

[edwintorok]

This works on Fedora 36+podman and Ubuntu 22.04+docker now, @connorgmeehan could you test again please and let me know if it works on your system?
I didn't make the :Z conditional for now because Docker understood and ignored that flag.

[edwintorok]

I pushed a few more docker fixes, including a script that can bootstrap nvim from a fresh dir, and another that just deletes the packer_compiled.lua to make testing changes easier.