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

fusl/src/time/mktime.c

Index: fusl/src/time/mktime.c
diff --git a/fusl/src/time/mktime.c b/fusl/src/time/mktime.c
new file mode 100644
index 0000000000000000000000000000000000000000..bad3f0765a089fd9f97e6f0d651b15fd19d949ed
--- /dev/null
+++ b/fusl/src/time/mktime.c
@@ -0,0 +1,28 @@
+#include "time_impl.h"
+#include <errno.h>
+
+time_t mktime(struct tm *tm)
+{
+	struct tm new;
+	long opp;
+	long long t = __tm_to_secs(tm);
+
+	__secs_to_zone(t, 1, &new.tm_isdst, &new.__tm_gmtoff, &opp, &new.__tm_zone);
+
+	if (tm->tm_isdst>=0 && new.tm_isdst!=tm->tm_isdst)
+		t -= opp - new.__tm_gmtoff;
+
+	t -= new.__tm_gmtoff;
+	if ((time_t)t != t) goto error;
+
+	__secs_to_zone(t, 0, &new.tm_isdst, &new.__tm_gmtoff, &opp, &new.__tm_zone);
+
+	if (__secs_to_tm(t + new.__tm_gmtoff, &new) < 0) goto error;
+
+	*tm = new;
+	return t;
+
+error:
+	errno = EOVERFLOW;
+	return -1;
+}