Fix `find` invocation in GitLab CI config

.gitlab-ci.yml

@@ -49,7 +49,7 @@ build_ext_projs:
   - if: '$CI_PIPELINE_SOURCE == "schedule"'
     when: always
   script:
-  - for d in $CI_PROJECT_DIR/ExternalProjects/*; do if [ -e "$d/build_release.sh" ] && (find "$d" -name '*.csproj' -maxdepth 1 -quit); then cd "$d" && ./build_release.sh; fi; done
+  - for d in $CI_PROJECT_DIR/ExternalProjects/*; do [ -e "$d/build_release.sh" -a "$(find "$d" -maxdepth 1 -name '*.csproj' -print -quit)" ] && cd "$d" && ./build_release.sh; fi; done
   stage: test
 
 build_ext_tools: