podman: configure network backend explicitly

Generate /etc/containers/containers.conf so Podman does not depend on
its internal default network backend at runtime.
If not, at runtime, the default podman network fails with:
"""
Error: could not find "netavark" in one of {[/usr/local/libexec/podman /usr/local/l
ib/podman /usr/libexec/podman /usr/lib/podman] {<nil>}}.  To resolve this error, se
t the helper_binaries_dir key in the `[engine]` section of containers.conf to the d
irectory containing your helper binaries.
"""

Signed-off-by: Isaac Hermida <isaac.hermida@digi.com>

meta-digi-containers/recipes-containers/podman/podman-trimmed_git.bb

@@ -9,6 +9,7 @@ DESCRIPTION = "Trimmed Podman runtime for dey-image-container-manager"
 # No CNI implies no isolated or custom network support, no NAT and no forwarding.
 # Host networking still works, and Podman uses netavark/aardvark-dns in this setup.
 VIRTUAL-RUNTIME_container_networking = ""
+PODMAN_NETWORK_BACKEND = "netavark"
 
 RDEPENDS:${PN}:append = " \
     netavark \

meta-digi-containers/recipes-containers/podman/podman_git.bbappend

@@ -0,0 +1,11 @@
+# Copyright (C) 2026, Digi International Inc.
+
+PODMAN_NETWORK_BACKEND ?= "${@('netavark' if d.getVar('VIRTUAL-RUNTIME_container_networking') == 'netavark' else 'cni')}"
+
+do_install:append() {
+    install -d ${D}${sysconfdir}/containers
+    cat > ${D}${sysconfdir}/containers/containers.conf <<EOF
+[network]
+network_backend="${PODMAN_NETWORK_BACKEND}"
+EOF
+}