CI: also build PX4 SITL without ninja

.ci/Jenkinsfile-compile

@@ -24,7 +24,7 @@ pipeline {
           ]
 
           def base_builds = [
-            target: ["px4_sitl_rtps"],
+            target: ["px4_sitl_rtps", "NO_NINJA_BUILD=1 px4_sitl_default"],
             image: docker_images.base,
             archive: false
           ]