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

fusl/src/thread/__tls_get_addr.c

Index: fusl/src/thread/__tls_get_addr.c
diff --git a/fusl/src/thread/__tls_get_addr.c b/fusl/src/thread/__tls_get_addr.c
new file mode 100644
index 0000000000000000000000000000000000000000..6945faa060d75ca66a5a4d3b01d34f1178b2cc9f
--- /dev/null
+++ b/fusl/src/thread/__tls_get_addr.c
@@ -0,0 +1,16 @@
+#include <stddef.h>
+#include "pthread_impl.h"
+#include "libc.h"
+
+__attribute__((__visibility__("hidden")))
+void *__tls_get_new(size_t *);
+
+void *__tls_get_addr(size_t *v)
+{
+	pthread_t self = __pthread_self();
+	if (v[0]<=(size_t)self->dtv[0])
+		return (char *)self->dtv[v[0]]+v[1]+DTP_OFFSET;
+	return __tls_get_new(v);
+}
+
+weak_alias(__tls_get_addr, __tls_get_new);