Fix file_extension extraction for Hyper-V cloud images

Handle compound hyperv.zip.* extensions in extract_file_extension
function to correctly identify file extensions for cloud images like
Armbian_*_minimal.hyperv.zip.xz

Signed-off-by: Igor Pecovnik <igor@armbian.com>

Author: igorpecovnik

scripts/generate-armbian-images-json.sh

@@ -412,6 +412,16 @@ extract_file_extension() {
     return
   fi
 
+  # hyperv cloud images: minimal.hyperv.zip.xz -> hyperv.zip.xz
+  if [[ "$n" == *".hyperv.zip."* ]]; then
+    echo "hyperv.zip.${n##*.hyperv.zip.}"
+    return
+  fi
+  if [[ "$n" == *.hyperv.zip ]]; then
+    echo "hyperv.zip"
+    return
+  fi
+
   # fallback
   echo "${n##*.}"
 }