Use sh-compatible version of redirection.

bin/blackbox_postdeploy

@@ -38,13 +38,12 @@ prepare_keychain
 
 # Decrypt:
 echo '========== Decrypting new/changed files: START'
-exec 99<"$BB_FILES"
-while read -u 99 unencrypted_file; do
+while IFS= read <&99 -r unencrypted_file; do
   encrypted_file=$(get_encrypted_filename "$unencrypted_file")
   decrypt_file_overwrite "$encrypted_file" "$unencrypted_file"
   chmod g+r "$unencrypted_file"
   if [[ ! -z "$FILE_GROUP" ]]; then
     chgrp $FILE_GROUP "$unencrypted_file"
   fi
-done
+done 99<"$BB_FILES"
 echo '========== Decrypting new/changed files: DONE'