Stop buildbot-build.sh script if any command fails

Bug: 142300164
Test: manual
Change-Id: Ie3f53f4f3917fe24554af3899ab905b0b6e5ea25
diff --git a/tools/buildbot-build.sh b/tools/buildbot-build.sh
index 2410164..240eaa6 100755
--- a/tools/buildbot-build.sh
+++ b/tools/buildbot-build.sh
@@ -14,6 +14,8 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+set -e
+
 if [ ! -d art ]; then
   echo "Script needs to be run at the root of the android tree"
   exit 1