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

fusl/src/stdio/__stdio_read.c

+#include "stdio_impl.h"
+#include <sys/uio.h>
+
+size_t __stdio_read(FILE *f, unsigned char *buf, size_t len)
+{
+        struct iovec iov[2] = {
+                { .iov_base = buf, .iov_len = len - !!f->buf_size },
+                { .iov_base = f->buf, .iov_len = f->buf_size }
+        };
+        ssize_t cnt;
+
+        cnt = syscall(SYS_readv, f->fd, iov, 2);
+        if (cnt <= 0) {
+                f->flags |= F_EOF ^ ((F_ERR^F_EOF) & cnt);
+                return cnt;
+        }
+        if (cnt <= iov[0].iov_len) return cnt;
+        cnt -= iov[0].iov_len;
+        f->rpos = f->buf;
+        f->rend = f->buf + cnt;
+        if (f->buf_size) buf[len-1] = *f->rpos++;
+        return len;
+}