Improve podman detection

Rather than checking if 'podman --version' runs, check if 'podman'
command exists.

In addition, distributions often provide a podman-docker package to have
the 'docker' command redirect to 'podman'. In such cases, we still need
to pass in podman-specific options for the containers to work.

Author: rnav

build/scripts/lib.sh

@@ -96,11 +96,11 @@ function get_default_version()
     return 0
 }
 
-podman --version > /dev/null
-if [[ $? -eq 0 ]]; then
-    DOCKER="podman"
-    PODMAN_OPTS="--security-opt label=disable --userns=keep-id"
-else
-    DOCKER="docker"
-    PODMAN_OPTS=""
+DOCKER="docker"
+PODMAN_OPTS=""
+if command -v podman > /dev/null; then
+    if (command -v docker && docker --version | grep -q podman) > /dev/null || ! command -v docker > /dev/null; then
+        DOCKER="podman"
+        PODMAN_OPTS="--security-opt label=disable --userns=keep-id"
+    fi
 fi