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

fusl/src/time/__tm_to_secs.c

+#include "time_impl.h"
+
+long long __tm_to_secs(const struct tm *tm)
+{
+        int is_leap;
+        long long year = tm->tm_year;
+        int month = tm->tm_mon;
+        if (month >= 12 || month < 0) {
+                int adj = month / 12;
+                month %= 12;
+                if (month < 0) {
+                        adj--;
+                        month += 12;
+                }
+                year += adj;
+        }
+        long long t = __year_to_secs(year, &is_leap);
+        t += __month_to_secs(month, is_leap);
+        t += 86400LL * (tm->tm_mday-1);
+        t += 3600LL * tm->tm_hour;
+        t += 60LL * tm->tm_min;
+        t += tm->tm_sec;
+        return t;
+}