cros_flash: Execute scripts out of /usr/local/tmp/cros-flash

Executing shell scripts from /mnt/stateful_partition is not supported
anymore. We need to use /usr/local instead.

BUG=chromium:1048049
TEST=cros flash

Change-Id: Ifd54815bac7ce1836e671db915691cbcf4ee48ce
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/2036452
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Tested-by: Amin Hassani <ahassani@chromium.org>
Commit-Queue: Amin Hassani <ahassani@chromium.org>
diff --git a/cli/flash.py b/cli/flash.py
index b1fae3a..7e7879a 100644
--- a/cli/flash.py
+++ b/cli/flash.py
@@ -341,7 +341,7 @@
   UPDATE_ENGINE_BIN = 'update_engine_client'
   # Root working directory on the device. This directory is in the
   # stateful partition and thus has enough space to store the payloads.
-  DEVICE_BASE_DIR = '/mnt/stateful_partition/cros-flash'
+  DEVICE_BASE_DIR = '/usr/local/tmp/cros-flash'
   UPDATE_CHECK_INTERVAL_PROGRESSBAR = 0.5
   UPDATE_CHECK_INTERVAL_NORMAL = 10