Looking through the elog output having just compiled gnome I see a very long list of unrecognized compile options (about 30 or so!) for app-misc/tracker-2.1.6-r1 implying that this package is not configured correctly.

It is probably worth looking at the following ebuild instead as a start-point for this package (which also shows that the available options have changed massively):

https://github.com/hhfeuer/Gentoo-Gnome-3.30-X/blob/master/app-misc/tracker/tracker-2.1.6.ebuild

btw) This is a funtoo-specific package, so this is not a gentoo bug.