Previously \r\n was used on Windows and \n was used on other
platforms. This resulted in different JSON content being written to
the archive. As the config's entry name is the SHA-256 hash of its
content, it also resulted in the entry name being different.

This commit updates the JSON that's written into the archive to use
\n line endings, irrespective of the OS on which the image is being
built.

See gh-19828