Build CircuitPython in a Github-Codespace

To build CircuitPython within a Github codespace, you need to perform the following steps.

checkout the code to a codespace

click on the green "<> Code"-button
select the Codespaces-tab
choose "+ new with options..." from the "..."-menu
in the following screen select the branch and then
select the port instead of "Default project configuration" (unsupported: ports not using cortex-m or esp-idf)
update region as necessary
finally, click on the green "Create codespace" button

Your codespace is created. Cloning the image and the repo is quite fast, but preparing it for CircuitPython-development takes about 10 minutes. But this is a one-time task: once created, your codespace exists until you explicitly delete it or until it times out (default: 30 days).
(Technical note: due to a bug in codespace creation, the setup is triggered from $HOME/.bashrc and runs in the background).
During creation, you can run the command tail -f /workspaces/install_build_env.log.active to see what is going on. Once finished the log file is available as /workspaces/install_build_env.log.
To actually build CircuitPython, open a new terminal and run e.g.
```
cd ports/raspberrypi
make -j $(nproc) BOARD=whatever TRANSLATION=xx_XX
```
This takes about 2m40s. The new terminal is necessary since the setup of the build environment also changes $HOME/.bashrc and sets important environment variables in that file.

As a normal user, you have 120 CPU-hours and 15GB per month free. Since the smallest machine has two CPUs, you effectively have 60 hours active time available.

All scripts are in circuitpython/.devcontainer and can also be executed manually which should usually not be necessary. With small changes, they should also work on a Linux-PC or laptop.