Update mikrotik_patch_7.yml

Signed-off-by: elseif <elseif@live.cn>

.github/workflows/mikrotik_patch_7.yml

@@ -300,6 +300,7 @@ jobs:
       run: |
         sudo modprobe nbd
         sudo apt-get install -y qemu-utils > /dev/null
+        truncate --size 128M chr-$LATEST_VERSION$ARCH.img
         sgdisk --clear --set-alignment=2 \
             --new=1::+32M --typecode=1:8300 --change-name=1:"RouterOS Boot" --attributes=1:set:2 \
             --new=2::-0 --typecode=2:8300 --change-name=2:"RouterOS" \