bug#40837: core-updates: webkitgtk web process sandbox incomplete

[Jack Hill]

I'm a little bit unstuck now. I found a bubblwrap issue [0], which I 
believe is the one that we're running into.

[0] https://github.com/containers/bubblewrap/issues/195 "Errors when 
--bind used with a symlinked path"

With insight gained there, I've determined that the following simplified 
bwrap invocation succeeds:

"""
$ bwrap  --ro-bind-try /etc/pulse/client.conf /etc/pulse/client.conf 
--ro-bind /gnu /gnu --ro-bind /run/current-system /run/current-system -- 
/run/current-system/profile/bin/bash
"""

while the following invocation fails:

"""
$ bwrap --ro-bind /etc /etc --ro-bind-try /etc/pulse/client.conf 
/etc/pulse/client.conf --ro-bind /gnu /gnu --ro-bind /run/current-system 
/run/current-system -- /run/current-system/profile/bin/bash

bwrap: Can't create file at /etc/pulse/client.conf: No such file or 
directory
"""

The difference between the working and non-working invocations in that in 
the non-working invocation, /etc is already mounted withing the new 
namespace, which includes symlinks at /etc/pulse and 
/etc/pulse/client.conf, and the later mount of the /etc/pulse/client.conf 
symlink causese the problem.

Now to figure out what the solution is, and if it is best fixed in 
webkitgtk or bubblewrap :)

Ideas welcome!

Best,
Jack