Add upgrade hooks for gdb SLOT problem

In older versions of gdb, we set SLOT=${CHOST}.
In the latest ones, we always set SLOT="0".
Since migrating SLOTs like this is not programmatic,
rewrite the installed values to 0 so that we can upgrade cleanly.

BUG=chromium-os:31356
TEST=None

Change-Id: Ieb4c5a25e1e28fcab64e2014c463c587023009a0
Reviewed-on: https://gerrit.chromium.org/gerrit/45399
Commit-Queue: Mike Frysinger <vapier@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
1 file changed