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

fusl/src/time/gmtime_r.c

Index: fusl/src/time/gmtime_r.c
diff --git a/fusl/src/time/gmtime_r.c b/fusl/src/time/gmtime_r.c
new file mode 100644
index 0000000000000000000000000000000000000000..8cbdadcb5d02164b845a7035dd68502ed794240b
--- /dev/null
+++ b/fusl/src/time/gmtime_r.c
@@ -0,0 +1,19 @@
+#include "time_impl.h"
+#include <errno.h>
+#include "libc.h"
+
+extern const char __gmt[];
+
+struct tm *__gmtime_r(const time_t *restrict t, struct tm *restrict tm)
+{
+	if (__secs_to_tm(*t, tm) < 0) {
+		errno = EOVERFLOW;
+		return 0;
+	}
+	tm->tm_isdst = 0;
+	tm->__tm_gmtoff = 0;
+	tm->__tm_zone = __gmt;
+	return tm;
+}
+
+weak_alias(__gmtime_r, gmtime_r);