[gnome-disk-utility] Build/install readme: Fix UDisks run command

[Kai Lüke <kailueke src gnome org>]

commit 60e062ba24744da7bf43324c5a5d533169ba8125
Author: Kai Lüke <kailueke riseup net>
Date:   Sat Aug 24 14:46:32 2019 +0200

    Build/install readme: Fix UDisks run command
    
    The previous LD_ trick to run the built UDisks
    did not fall back to the runtime's libraries
    when they couldn't be found on the system.
    
    Use bwrap to set up the same environment
    Flatpak uses with the runtime mounted as well,
    so that we never use system libraries.

 INSTALL | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
---
diff --git a/INSTALL b/INSTALL
index 888bf871..b0fb9535 100644
--- a/INSTALL
+++ b/INSTALL
@@ -45,7 +45,8 @@ replacing the system daemon:
 
 Using Flatpak to build and run GNOME Disks and UDisks (both from web sources):
   flatpak-builder app flatpak/org.gnome.DiskUtility.json
-  sudo LD_LIBRARY_PATH=app/files/lib/ app/files/libexec/udisks2/udisksd -r
+  # now run UDisks as system service, replacing your system's instance
+  sudo bwrap --tmpfs / --proc /proc --bind /sys /sys --dev-bind /dev /dev --dir /tmp --ro-bind 
/home/kai/.local/share/flatpak/runtime/org.gnome.Platform/x86_64/master/active/files /usr --bind /etc /etc 
--bind /var /var --bind /run /run --symlink usr/lib64 /lib64 --ro-bind app/files /app --chdir / 
--die-with-parent /app/libexec/udisks2/udisksd -r
   # in a new terminal in the current folder:
   flatpak-builder --run app flatpak/org.gnome.DiskUtility.json gnome-disks
   # or LD_LIBRARY_PATH=app/files/lib/ app/files/bin/gnome-disks to run without any sandboxing