fix(ci): point LG_ENV at -dual-tftp target when staging kernel + ramdisk

[francoriba]

Context

Follow-up to libremesh/libremesh-tests#5 which splits the LibreRouter v1 target YAML into two variants:

• targets/librerouter_librerouter-v1.yaml - single-image (default)
• targets/librerouter_librerouter-v1-dual-tftp.yaml - kernel + rootfs uImage

Reason for the split: the single-image variant is what mesh tests, LibreMesh releases and openwrt-tests healthcheck actually use (initramfs-kernel.bin, only LG_IMAGE set). The previous librerouter YAML required both LG_IMAGE and LG_IMAGE_INITRD unconditionally, breaking every non-dual flow.

Problem in this CI

build-firmware.yml pre-sets LG_ENV=targets/${{ matrix.device }}.yaml in the labgrid lock step. After the split, that points at the single-image variant.

When lab_stage_firmware.sh then detects the dual-tftp payload (bin + uimage pair produced by build_image.sh for devices like the LibreRouter v1 on ath79), it exports LG_IMAGE_INITRD — but the single-image YAML does not reference that variable, so labgrid loads only the kernel and boot fails without a rootfs.

Fix

When lab_stage_firmware.sh enters the dual-TFTP branch, override LG_ENV with the -dual-tftp sibling target file so labgrid resolves LG_IMAGE_INITRD and issues both TFTP loads.

DUAL_ENV="targets/${DEVICE}-dual-tftp.yaml"
echo "LG_ENV=$DUAL_ENV" >> "$GITHUB_ENV"

No change for single-image devices (openwrt_one, linksys_e8450, bananapi_bpi-r4, qemu_*): the else branch keeps the pre-set LG_ENV.

Depends on

• libremesh/libremesh-tests#5 - merge first so the -dual-tftp target file exists in the checked-out libremesh-tests.

[francoriba]

Redirigido al repo upstream libremesh/lime-packages en el PR nuevo.