librem5-devkit-tools: Fix arch
Although it doesn't matter which arch we use use arm64 since that's what we intended to do in the last commit.
Due to an influx of spam, we have had to impose restrictions on new accounts. Please see this wiki page for instructions on how to get full permissions. Sorry for the inconvenience.
Although it doesn't matter which arch we use use arm64 since that's what we intended to do in the last commit.