The content-type for the gzip files we make available for download is application/x-gzip. This causes problems with some browsers that don't understand this content type.

According to RFC6648 the x- types are deprecated, and RFC6713 says the right type for gzip files is application/gzip.

The work in this ticket has two parts:

• Update evergreen.yml to use the right content type for new files
• Update the existing files to have the right content type