ci/build.sh: fail if trying to use an unset variable

diff --git a/ci/build.sh b/ci/build.sh
index 326ca257d0ce5de52ac9b06b65f9dcbbd3d81377..10d4f68222fe3145048643d3267ed677fc581bb7 100755 (executable)
--- a/ci/build.sh
+++ b/ci/build.sh
@@ -2,6 +2,7 @@
 
 set -x
 set -e
+set -u
 set -o pipefail
 
 if [ -f /etc/os-release ]; then