Just a note that that the BuildOnLinux documents in the 0.8.900 pre-release have some typos in them. They've been fixed (I think!), and some additions have been made in the current source tree.
Those changes will make it into the next release, but in the meantime ... Linux users should use the BuildingOnLinux.md file on github if they run into trouble. You can browse it directly if you like.
https://github.com/Sigil-Ebook/Sigil...dingOnLinux.md
But please don't build Sigil from a current git clone right now. There are issues being resolved. Build from the tagged source that is downloadable from the Releases page.
Linux users are encouraged to build from the current github source tree.