see if threads.h is there

trythrds.c

@@ -0,0 +1,25 @@
+#include <sys/time.h>
+#include <threads.h>
+
+int worker(void* arg) {
+  (void)arg;
+  return 0;
+}
+
+int main() {
+  thrd_t x;
+  if (thrd_create(&x,worker,0)==-1)
+    return 111;
+  if (thrd_join(x,NULL)==-1)
+    return 111;
+  cnd_t c;
+  mtx_t m;
+  mtx_init(&m, mtx_plain);
+  mtx_lock(&m);
+  mtx_unlock(&m);
+  cnd_init(&c);
+  cnd_timedwait(&c, &m, (struct timespec[]){ [0].tv_sec=1 });
+  cnd_destroy(&c);
+  mtx_destroy(&m);
+  return 0;
+}