Add a "fork" of musl as //fusl.

fusl/src/time/timer_settime.c

Index: fusl/src/time/timer_settime.c
diff --git a/fusl/src/time/timer_settime.c b/fusl/src/time/timer_settime.c
new file mode 100644
index 0000000000000000000000000000000000000000..62631aa49cda75f49fba047163747cd29faa60e3
--- /dev/null
+++ b/fusl/src/time/timer_settime.c
@@ -0,0 +1,12 @@
+#include <time.h>
+#include <limits.h>
+#include "pthread_impl.h"
+
+int timer_settime(timer_t t, int flags, const struct itimerspec *restrict val, struct itimerspec *restrict old)
+{
+	if ((intptr_t)t < 0) {
+		pthread_t td = (void *)((uintptr_t)t << 1);
+		t = (void *)(uintptr_t)(td->timer_id & INT_MAX);
+	}
+	return syscall(SYS_timer_settime, t, flags, val, old);
+}