feat: add NTP; fix networking bugs/regressions

programs/include/montauk/syscall.h

@@ -367,6 +367,9 @@ namespace montauk {
 
     // Timekeeping (wall-clock)
     inline void gettime(montauk::abi::DateTime* out) { syscall1(montauk::abi::SYS_GETTIME, (uint64_t)out); }
+    inline int set_unix_time(int64_t unix_seconds) {
+        return (int)syscall1(montauk::abi::SYS_SETUNIXTIME, (uint64_t)unix_seconds);
+    }
 
     // Timezone offset (total minutes from UTC)
     inline void settz(int offset_minutes) { syscall1(montauk::abi::SYS_SETTZ, (uint64_t)(int64_t)offset_minutes); }