v4.19.13 snapshot.
diff --git a/tools/build/feature/test-setns.c b/tools/build/feature/test-setns.c
new file mode 100644
index 0000000..1f714d2
--- /dev/null
+++ b/tools/build/feature/test-setns.c
@@ -0,0 +1,7 @@
+#define _GNU_SOURCE
+#include <sched.h>
+
+int main(void)
+{
+	return setns(0, 0);
+}