Comment 4 for bug 1517257

Idea from sprint discussion:

In apport:
 - Don't try to run gdb from the retracing target sandbox

 - Add --gdb-root <path> argument to apport-retrace that will set PATH, LD_LIBRARY_PATH, and possibly some env var to specify the gdb plugin dir to appropriate subdirs of <path>. Calling "gdb" should then prefer running gdb from that dir.

In the retracer deployment:
 - add --gdb-root on the sandbox with the same release but the host's native architecture
 - Ensure that gdb is installed in that