initenv.sh on MacOS fails (crypt_r build error)

MacOS no longer ships a libcrypt as required by crypt_r, so you need to install one. If you use Brew this will work:

```shell
brew install libxcrypt
env LDFLAGS="-L$(brew --prefix libxcrypt)/lib" CFLAGS="-I$(brew --prefix libxcrypt)/include" ./scripts/initenv.sh
```

Now you have a working venv for doing the cmdeploy.

Start by reproducing the macOS failure with scripts/initenv.sh and read how it builds the Python environment for cmdeploy. Check whether the issue calls for changing the script or documenting the libxcrypt and Homebrew prerequisite; done means a macOS environment initializes successfully without the crypt_r build error.

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