WIP: Fix ssh_client build.sh script

+ Switch SDK version to latest M25
+ Update build scripts to work with current naclports
+ Pin naclports to fixed revision

TODO: Update part of the script that copy hterm files.
TODO: Resolve issue with PNaCl toolchain crash.

BUG=none
TEST=manual

Change-Id: I2e5af88a79cc7721dabd135582ef381d09ed73bc