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

fusl/src/stat/mkdir.c

Index: fusl/src/stat/mkdir.c
diff --git a/fusl/src/stat/mkdir.c b/fusl/src/stat/mkdir.c
new file mode 100644
index 0000000000000000000000000000000000000000..32625b7de32768dc45916b76c0d063af89e1203c
--- /dev/null
+++ b/fusl/src/stat/mkdir.c
@@ -0,0 +1,12 @@
+#include <sys/stat.h>
+#include <fcntl.h>
+#include "syscall.h"
+
+int mkdir(const char *path, mode_t mode)
+{
+#ifdef SYS_mkdir
+	return syscall(SYS_mkdir, path, mode);
+#else
+	return syscall(SYS_mkdirat, AT_FDCWD, path, mode);
+#endif
+}