Fail the build if one step fails

Fail the build if one step fails

Setting this option in the bash script will cause the
script to terminate if any of the commands returns a
with non-zero value.  This is necessary for the build
server to understand when a build is failed.  Without this
flag, the script will exit with the status of the last command,
which in this script is "echo" so it will be 0, regardless if
a scons build step failed.

Ideally we would try each step and then report the failures
at the end, set -e will do the job until that can be developed.

Change-Id: Ib6692d434a2e811f61d8dd1bff52766b7511abd7
Signed-off-by: David Warburton <david.warburton@intel.com>