contrib: add check for wget command in install_db4.sh

contrib/install_db4.sh

@@ -55,8 +55,11 @@ http_get() {
     echo "File ${2} already exists; not downloading again"
   elif check_exists curl; then
     curl --insecure --retry 5 "${1}" -o "${2}"
-  else
+  elif check_exists wget; then
     wget --no-check-certificate "${1}" -O "${2}"
+  else
+    echo "Simple transfer utilities 'curl' and 'wget' not found. Please install one of them and try again."
+    exit 1
   fi
 
   sha256_check "${3}" "${2}"