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

fusl/src/stdio/tmpfile.c

+#include <stdio.h>
+#include <fcntl.h>
+#include "stdio_impl.h"
+
+#define MAXTRIES 100
+
+char *__randname(char *);
+
+FILE *tmpfile(void)
+{
+        char s[] = "/tmp/tmpfile_XXXXXX";
+        int fd;
+        FILE *f;
+        int try;
+        for (try=0; try<MAXTRIES; try++) {
+                __randname(s+13);
+                fd = sys_open(s, O_RDWR|O_CREAT|O_EXCL, 0600);
+                if (fd >= 0) {
+#ifdef SYS_unlink
+                        __syscall(SYS_unlink, s);
+#else
+                        __syscall(SYS_unlinkat, AT_FDCWD, s, 0);
+#endif
+                        f = __fdopen(fd, "w+");
+                        if (!f) __syscall(SYS_close, fd);
+                        return f;
+                }
+        }
+        return 0;
+}
+
+LFS64(tmpfile);