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

fusl/src/temp/mkostemps.c

+#define _BSD_SOURCE
+#include <string.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <errno.h>
+#include "libc.h"
+
+char *__randname(char *);
+
+int __mkostemps(char *template, int len, int flags)
+{
+        size_t l = strlen(template);
+        if (l<6 || len>l-6 || memcmp(template+l-len-6, "XXXXXX", 6)) {
+                errno = EINVAL;
+                return -1;
+        }
+
+        flags -= flags & O_ACCMODE;
+        int fd, retries = 100;
+        do {
+                __randname(template+l-len-6);
+                if ((fd = open(template, flags | O_RDWR | O_CREAT | O_EXCL, 0600))>=0)
+                        return fd;
+        } while (--retries && errno == EEXIST);
+
+        memcpy(template+l-len-6, "XXXXXX", 6);
+        return -1;
+}
+
+weak_alias(__mkostemps, mkostemps);
+weak_alias(__mkostemps, mkostemps64);