Attempt to install a version in asdf 0.7.* results in /** being moved to $ASDF_INSTALL_PATH

[richin13]

Description

As of now the plugin is not backwards compatible with asdf version 0.7.*.

From asdf-vm/asdf#765 (comment)

If you want your plugin to work with both versions of asdf (0.8.* and 0.7.*) check for the presence of the ASDF_DOWNLOAD_PATH environment variable, and if it is not set download the qt code in the bin/install callback, and if it is set then assume the bin/download script already downloaded it (sounds like you've already implemented bin/download properly).

Right now we're not checking for the existence of $ASDF_DOWNLOAD_PATH in bin/install and just assume it exists which results in the root folder being moved to $ASDF_INSTALL_PATH