mkimg_gpt.sh: standard filename, overwrite support, better extlinux label

- Output filename now uses LINEAGE_VERSION env var from lunch,
  producing lineage-23.2-20260711-UNOFFICIAL-orangepi5ultra.img
- Overwrite existing files instead of failing
- extlinux.conf label changed to 'LineageOS Android TV'

Copyright (C) 2026 Brendan Szymanski <hello@bscubed.dev>

mkimg_gpt.sh

@@ -50,15 +50,13 @@ if [ ! -f "${UBOOT_BIN}" ]; then
   exit_with_error "Missing U-Boot: ${UBOOT_BIN}"
 fi
 
-VERSION=OrangePi_5Ultra_lineage_atv
-DATE=$(date +%Y%m%d)
-TARGET=$(echo "${TARGET_PRODUCT}" | sed 's/^aosp_//')
-IMGNAME=${VERSION}-${DATE}-${TARGET}_gpt.img
+: "${LINEAGE_VERSION:?LINEAGE_VERSION environment variable is not set. Run lunch first.}"
 IMGSIZE=19456MiB
-IMAGE_PATH="${ANDROID_PRODUCT_OUT}/${IMGNAME}"
+IMAGE_PATH="${ANDROID_PRODUCT_OUT}/lineage-${LINEAGE_VERSION}.img"
 
 if [ -f "${IMAGE_PATH}" ]; then
-  exit_with_error "${IMAGE_PATH} already exists!"
+  echo "Overwriting existing image: ${IMAGE_PATH}"
+  sudo rm -f "${IMAGE_PATH}"
 fi
 
 echo "Creating image file ${IMAGE_PATH} (${IMGSIZE})..."
@@ -130,7 +128,7 @@ sudo cp ${KERNEL_PATH}/Image "${BOOT_MOUNT}/"
 sudo cp ${KERNEL_PATH}/rk3588-orangepi-5-ultra.dtb "${BOOT_MOUNT}/"
 sudo mkdir -p "${BOOT_MOUNT}/extlinux"
 sudo tee "${BOOT_MOUNT}/extlinux/extlinux.conf" > /dev/null << 'EXTLINUX_EOF'
-label Android TV
+label LineageOS Android TV
     kernel /Image
     fdt /rk3588-orangepi-5-ultra.dtb
     initrd /ramdisk.img