Create a tool for downloading

Wrap curl inside a function that tries to download at least three times. Use that in hunspell and also check that the zip files are consistent.

scripts/hunspell.sh

@@ -6,7 +6,9 @@ function action3_hunspell ()
     if test -f "$hunspell_zip_file"; then
         echo File $hunspell_zip_file already exists.
     else
-        curl -L "$hunspell_link" > $hunspell_zip_file
+        try_download "$hunspell_link" "$hunspell_zip_file" \
+            && test -f "$hunspell_zip_file" \
+            && unzip -t "$hunspell_zip_file"
         if test "$?" != 0; then
             echo Unable to download Hunspell from
             echo "  $hunspell_link"

scripts/tools.sh

@@ -186,3 +186,18 @@ function prepare_build_dir ()
         mkdir -p "$build_dir"
     fi
 }
+
+function try_download ()
+{
+    local url="$1"
+    local destination="$2"
+    local attempts="$3"
+    if [ -z "$attempts" ]; then
+        attempts=3
+    fi
+    while [ $attempts -gt 0 ]; then
+        curl --progress-bar --retry 3 --output "$destination" "$url" && return 0
+        attempts=$(($attempts - 1))
+    fi
+    return -1
+}