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

fusl/src/dirent/seekdir.c

Index: fusl/src/dirent/seekdir.c
diff --git a/fusl/src/dirent/seekdir.c b/fusl/src/dirent/seekdir.c
new file mode 100644
index 0000000000000000000000000000000000000000..5be47d4a15564178eb84e73a0d9a9569fd8b30b3
--- /dev/null
+++ b/fusl/src/dirent/seekdir.c
@@ -0,0 +1,12 @@
+#include <dirent.h>
+#include <unistd.h>
+#include "__dirent.h"
+#include "libc.h"
+
+void seekdir(DIR *dir, long off)
+{
+	LOCK(dir->lock);
+	dir->tell = lseek(dir->fd, off, SEEK_SET);
+	dir->buf_pos = dir->buf_end = 0;
+	UNLOCK(dir->lock);
+}