Fix X11 library underlinking, which was breaking Debian and Ubuntu
packages.
From Ubuntu Hirsute changelog:
```
blender (2.83.5+dfsg-4ubuntu1) hirsute; urgency=medium
* Try to also link ghost library with x11, needed because of missing
XConvertSelection symbol link (used in ghost static library).
* Don't use gold, but switch to bfd linker that seems to be working better
on ppc64el.
-- Gianfranco Costamagna <locutusofborg@debian.org> Wed, 11 Nov 2020 14:17:29 +0100
```
Reviewed by: sybren
Differential Revision: https://developer.blender.org/D9617
9258b70453