Following these instructions does not fix the problem:

cel900 /home/haxmeister # emerge -a freecad

These are the packages that would be merged, in order:

Calculating dependencies... done!

The following mask changes are necessary to proceed:
(see "package.unmask" in the portage(5) man page for more details)

1. required by freecad (argument)
2. /var/git/meta-repo/kits/core-kit/profiles/package.mask/00-gentoo:
3. Andreas Sturmlechner <asturm@gentoo.org> (16 Nov 2017)
4. Depends on dead Qt4WebKit. Masked for removal in 30 days. Bug #620702
   =media-gfx/freecad-0.17_pre

NOTE: The --autounmask-keep-masks option will prevent emerge
from creating package.unmask or ** keyword changes.

Would you like to add these changes to your config files? [Yes/No] n

• In order to avoid wasting time, backtracking has terminated early
• due to the above autounmask change(s). The --autounmask-backtrack=y
• option can be used to force further backtracking, but there is no
• guarantee that it will produce a solution.

emerge: there are no ebuilds to satisfy "dev-qt/qtwebkit:4".
(dependency required by "media-gfx/freecad-0.17_pre::media-kit" [ebuild])
(dependency required by "freecad" [argument])