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

fusl/src/unistd/usleep.c

Index: fusl/src/unistd/usleep.c
diff --git a/fusl/src/unistd/usleep.c b/fusl/src/unistd/usleep.c
new file mode 100644
index 0000000000000000000000000000000000000000..6c96652691e0dabacacde4885f74466d2772a661
--- /dev/null
+++ b/fusl/src/unistd/usleep.c
@@ -0,0 +1,12 @@
+#define _GNU_SOURCE
+#include <unistd.h>
+#include <time.h>
+
+int usleep(unsigned useconds)
+{
+	struct timespec tv = {
+		.tv_sec = useconds/1000000,
+		.tv_nsec = (useconds%1000000)*1000
+	};
+	return nanosleep(&tv, &tv);
+}