Add support for using podman to util/docker_build.sh (#10819)

* add podman support to docker_build.sh script

* break out runtime into the RUNTIME variable
* allows RUNTIME to be set by the user
* decides on docker or podman if docker isn't avaible
* rewrote check for docker-machine to account only for docker runtime
* put --user arg into a variable only to be used with docker
  this is not needed with podman as podman maps the containers root id
  to the users id.

* add podman to getting_started_docker documentation

2 files changed, 39 insertions, 10 deletions

diff --git a/docs/getting_started_docker.md b/docs/getting_started_docker.md
index e5309fdbb..f9c3b366a 100644
--- a/docs/getting_started_docker.md
+++ b/docs/getting_started_docker.md
@@ -4,8 +4,9 @@ This project includes a Docker workflow that will allow you to build a new firmw
 
 ## Requirements
 
-The main prerequisite is a working `docker` install.
+The main prerequisite is a working `docker` or `podman` install.
 * [Docker CE](https://docs.docker.com/install/#supported-platforms)
+* [Podman](https://podman.io/getting-started/installation)
 
 ## Usage
 
@@ -38,6 +39,13 @@ util/docker_build.sh
 # Reads parameters as input (leave blank for all keyboards/keymaps)
 ```
 
+You can manually set which container runtime you want to use by setting the `RUNTIME` environment variable to it's name or path.
+By default docker or podman are automatically detected and docker is preferred over podman.
+
+```bash
+RUNTIME="podman" util/docker_build.sh keyboard:keymap:target
+```
+
 ## FAQ
 
 ### Why can't I flash on Windows/macOS
diff --git a/util/docker_build.sh b/util/docker_build.sh
index bf13f5097..2b109be76 100755
--- a/util/docker_build.sh
+++ b/util/docker_build.sh
@@ -17,12 +17,27 @@ done
 if [ $# -gt 1 ]; then
         errcho "$USAGE"
         exit 1
-elif ! command -v docker >/dev/null 2>&1; then
-        errcho "Error: docker not found"
-        errcho "See https://docs.docker.com/install/#supported-platforms for installation instructions"
-        exit 2
 fi
 
+# Allow $RUNTIME to be overriden by the user as an environment variable
+# Else check if either docker or podman exit and set them as runtime
+# if none are found error out
+if [ -z "$RUNTIME" ]; then
+        if command -v docker >/dev/null 2>&1; then
+                RUNTIME="docker"
+        elif command -v podman >/dev/null 2>&1; then
+                RUNTIME="podman"
+        else
+                errcho "Error: no compatible container runtime found."
+                errcho "Either podman or docker are required."
+                errcho "See https://podman.io/getting-started/installation"
+                errcho "or https://docs.docker.com/install/#supported-platforms"
+                errcho "for installation instructions."
+                exit 2
+        fi
+fi
+        
+
 # Determine arguments
 if [ $# -eq 0 ]; then
         printf "keyboard=" && read -r keyboard
@@ -41,20 +56,26 @@ if [ -z "$keyboard" ]; then
         keyboard=all
 fi
 if [ -n "$target" ]; then
-        if [ "$(uname)" = "Linux" ] || docker-machine active >/dev/null 2>&1; then
-                usb_args="--privileged -v /dev:/dev"
-        else
+        # IF we are using docker on non Linux and docker-machine isn't working print an error
+        # ELSE set usb_args
+        if [ ! "$(uname)" = "Linux" ] && [ "$RUNTIME" = "docker" ] && ! docker-machine active >/dev/null 2>&1; then
                 errcho "Error: target requires docker-machine to work on your platform"
                 errcho "See http://gw.tnode.com/docker/docker-machine-with-usb-support-on-windows-macos"
                 errcho "Consider flashing with QMK Toolbox (https://github.com/qmk/qmk_toolbox) instead"
                 exit 3
+        else
+                usb_args="--privileged -v /dev:/dev"
         fi
 fi
 dir=$(pwd -W 2>/dev/null) || dir=$PWD  # Use Windows path if on Windows
 
+if [ "$RUNTIME" = "docker" ]; then
+        uid_arg="--user $(id -u):$(id -g)"
+fi
+
 # Run container and build firmware
-docker run --rm -it $usb_args \
-        --user $(id -u):$(id -g) \
+"$RUNTIME" run --rm -it $usb_args \
+        $uid_arg \
         -w /qmk_firmware \
         -v "$dir":/qmk_firmware \
         -e ALT_GET_KEYBOARDS=true \