workflows: add custom template path

With the addition of the meta-balena-hab submodule there are multiple
balena layers with custom templates - specify which one to use to avoid
a build error.

Changelog-entry: add custom template path to iot-gate-imx8
Signed-off-by: Alex Gonzalez <[email protected]>

Author: alexgg

.github/workflows/iot-gate-imx8.yml

@@ -50,6 +50,7 @@ jobs:
     secrets: inherit
     with:
       machine: iot-gate-imx8
+      build-args: '--templates-path layers/meta-balena-imx8mm'
       # worker_type defaults to testbot
       # worker_fleets defaults to balena/testbot-rig,balena/testbot-rig-partners,balena/testbot-rig-x86,balena/testbot-rig-partners-x86
       test_matrix: >