linux: improve FUSE support

This fixes a number of AppImages; tested with
scribus-1.5.6.1-linux-x86_64.AppImage.

Reported By: @probonopd
Reviewed By: asomers, emaste
Sponsored By: EPSRC
Differential Revision: https://reviews.freebsd.org/D30606

(cherry picked from commit 128a1db806daac088a79314cee060b8a204e8481)