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

fusl/src/misc/realpath.c

+#include <stdlib.h>
+#include <limits.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <unistd.h>
+#include <string.h>
+#include "syscall.h"
+
+void __procfdname(char *, unsigned);
+
+char *realpath(const char *restrict filename, char *restrict resolved)
+{
+        int fd;
+        ssize_t r;
+        struct stat st1, st2;
+        char buf[15+3*sizeof(int)];
+        char tmp[PATH_MAX];
+
+        if (!filename) {
+                errno = EINVAL;
+                return 0;
+        }
+
+        fd = sys_open(filename, O_PATH|O_NONBLOCK|O_CLOEXEC);
+        if (fd < 0) return 0;
+        __procfdname(buf, fd);
+
+        r = readlink(buf, tmp, sizeof tmp - 1);
+        if (r < 0) goto err;
+        tmp[r] = 0;
+
+        fstat(fd, &st1);
+        r = stat(tmp, &st2);
+        if (r<0 || st1.st_dev != st2.st_dev || st1.st_ino != st2.st_ino) {
+                if (!r) errno = ELOOP;
+                goto err;
+        }
+
+        __syscall(SYS_close, fd);
+        return resolved ? strcpy(resolved, tmp) : strdup(tmp);
+err:
+        __syscall(SYS_close, fd);
+        return 0;
+}