pkg/debug: fix spec.sh to print valid json

`print_usb_devices` now uses the `$COMMA` mechanism to add a
comma after every device

Signed-off-by: Christoph Ostarek <christoph@zededa.com>

Author: christoph-zededa

pkg/debug/Dockerfile

@@ -120,6 +120,10 @@ SHELL ["/bin/ash", "-eo", "pipefail", "-c"]
 # Ensure that the output of spec.sh is valid json
 RUN ./usr/bin/spec.sh -v 2>/dev/null | jq . > /dev/null
 RUN ./usr/bin/spec.sh 2>/dev/null | jq . > /dev/null
+RUN mkdir /tmp/bin
+COPY tests/lsusb /tmp/bin
+RUN chmod a+x /tmp/bin/lsusb
+RUN PATH=/tmp/bin:$PATH /out/usr/bin/spec.sh -u 2>/dev/null | jq .
 
 RUN mkdir -p ./etc/ssh ./root/.ssh
 RUN chmod 0700 ./root/.ssh

pkg/debug/spec.sh

@@ -383,6 +383,7 @@ print_usb_devices() {
         fi
 
         cat <<__EOT__
+    ${COMMA}
     {
       "ztype": "${ztype}",
       "phylabel": "${label}",
@@ -395,8 +396,8 @@ print_usb_devices() {
       },
       "logicallabel": "$label",
       "usagePolicy": {}
-    },
 __EOT__
+    COMMA="},"
     done
 }
 

pkg/debug/tests/lsusb

@@ -0,0 +1,8 @@
+#!/bin/sh
+
+# Copyright (c) 2026 Zededa, Inc.
+# SPDX-License-Identifier: Apache-2.0
+
+echo "Bus 001 Device 001: ID 1d6b:0002 Linux 6.12.49-linuxkit-core-ef7ccc4d151c xhci-hcd xHCI Host Controller"
+echo "Bus 002 Device 002: ID 46f4:0001 QEMU QEMU USB HARDDRIVE"
+echo "Bus 002 Device 001: ID 1d6b:0003 Linux 6.12.49-linuxkit-core-ef7ccc4d151c xhci-hcd xHCI Host Controller"