Update int.cloudbuild.yaml

Author: apeabody

build/int.cloudbuild.yaml

@@ -38,8 +38,8 @@ steps:
       _INFRA_FOLDERS="build test .github"
       while read d; do
         echo "${d%/}"
-        if [[ ${_INFRA_FOLDERS} =~ ${d%/} ]]; then
-          echo "Infrastructure folder ${d%/} has changed; no tests will be pruned."
+        if [[ "${_INFRA_FOLDERS}" =~ "$d%/" ]]; then
+          echo "Infrastructure folder $d%/ has changed; no tests will be pruned."
           exit 0 # do not prune
         fi
       done < _changed_folders