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

fusl/src/time/localtime_r.c

Index: fusl/src/time/localtime_r.c
diff --git a/fusl/src/time/localtime_r.c b/fusl/src/time/localtime_r.c
new file mode 100644
index 0000000000000000000000000000000000000000..2e62c29fb2ac1bccaf5af0f045a5bbf5ffefc880
--- /dev/null
+++ b/fusl/src/time/localtime_r.c
@@ -0,0 +1,21 @@
+#include "time_impl.h"
+#include <errno.h>
+#include "libc.h"
+
+struct tm *__localtime_r(const time_t *restrict t, struct tm *restrict tm)
+{
+	/* Reject time_t values whose year would overflow int because
+	 * __secs_to_zone cannot safely handle them. */
+	if (*t < INT_MIN * 31622400LL || *t > INT_MAX * 31622400LL) {
+		errno = EOVERFLOW;
+		return 0;
+	}
+	__secs_to_zone(*t, 0, &tm->tm_isdst, &tm->__tm_gmtoff, 0, &tm->__tm_zone);
+	if (__secs_to_tm((long long)*t + tm->__tm_gmtoff, tm) < 0) {
+		errno = EOVERFLOW;
+		return 0;
+	}
+	return tm;
+}
+
+weak_alias(__localtime_r, localtime_r);