utils/docker-run: allow running with Podman

Podman is command line compatible with Docker, there's no need to
require contributors to install Docker to run checks before sending
patches.

The additional "--userns=keep-id" option is necessary because unlike
Docker Podman creates a user namespace for containers by
default. Without keep-id the repository and pre-existing output files
belong to root inside the container namespace, breaking writes,
certain Git safety checks, and possibly all access (if the user is
using a strict umask).

Signed-off-by: Fiona Klute <fiona.klute+wiwa@gmx.de>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>

utils/docker-run

@@ -29,6 +29,16 @@ declare -a mountpoints=(
     "$(pwd)"
 )
 
+if command -v docker >/dev/null; then
+    DOCKER="docker"
+elif command -v podman >/dev/null; then
+    DOCKER="podman"
+    docker_opts+=( --userns=keep-id )
+else
+    echo "ERROR: Neither docker nor podman available!" >&2
+    exit 1
+fi
+
 # curl lists (and recognises and uses) other types of *_proxy variables,
 # but only those make sense for Buildroot:
 for env in all_proxy http_proxy https_proxy ftp_proxy no_proxy; do
@@ -84,4 +94,4 @@ if tty -s; then
     docker_opts+=( -t )
 fi
 
-exec docker run "${docker_opts[@]}" "${IMAGE}" "${@}"
+exec ${DOCKER} run "${docker_opts[@]}" "${IMAGE}" "${@}"