Make the Jenkins script print which command it's running

This means you can reproduce failures without having to guess which
command failed.

Change-Id: I3dfea4b06dcf06c4e911e373961cb4ace01d9365
diff --git a/tools/ci/run-tests.sh b/tools/ci/run-tests.sh
index 6b7414f..5e31caa 100755
--- a/tools/ci/run-tests.sh
+++ b/tools/ci/run-tests.sh
@@ -1,5 +1,6 @@
 #!/bin/sh
 set -e
+set -x
 
 bazel --batch test -c opt --curses=no --color=no //...
 bazel --batch build -c opt --curses=no --color=no //... --cpu=roborio