set -e in place, rely on output rather than exit codes

Author: glasnt

build/int.cloudbuild.yaml

@@ -35,9 +35,8 @@ steps:
       cat _changed_folders
 
       # Do not prune if changing tests themselves
-      git diff --quiet origin/main build test .github/workflows
-      _CHANGED=$?
-      if [[ "${_CHANGED}" -ne 0 ]]; then
+      _build_changes=$(git diff --quiet origin/main build test .github/workflows)
+      if [[ -n "${_build_changes}" ]]; then
           echo "Infrastructure folders have changed; no tests will be pruned."
           exit 0 # do not prune
       fi