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

fusl/src/linux/adjtime.c

+#define _GNU_SOURCE
+#include <sys/time.h>
+#include <sys/timex.h>
+#include <errno.h>
+#include "syscall.h"
+
+int adjtime(const struct timeval *in, struct timeval *out)
+{
+        struct timex tx = { 0 };
+        if (in) {
+                if (in->tv_sec > 1000 || in->tv_usec > 1000000000) {
+                        errno = EINVAL;
+                        return -1;
+                }
+                tx.offset = in->tv_sec*1000000 + in->tv_usec;
+                tx.modes = ADJ_OFFSET_SINGLESHOT;
+        }
+        if (syscall(SYS_adjtimex, &tx) < 0) return -1;
+        if (out) {
+                out->tv_sec = tx.offset / 1000000;
+                if ((out->tv_usec = tx.offset % 1000000) < 0) {
+                        out->tv_sec--;
+                        out->tv_usec += 1000000;
+                }
+        }
+        return 0;
+}