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

fusl/src/thread/pthread_join.c

Index: fusl/src/thread/pthread_join.c
diff --git a/fusl/src/thread/pthread_join.c b/fusl/src/thread/pthread_join.c
new file mode 100644
index 0000000000000000000000000000000000000000..694d377ad486b834bf3c8453ed092ab684fd1fc9
--- /dev/null
+++ b/fusl/src/thread/pthread_join.c
@@ -0,0 +1,22 @@
+#include "pthread_impl.h"
+#include <sys/mman.h>
+
+int __munmap(void *, size_t);
+void __pthread_testcancel(void);
+int __pthread_setcancelstate(int, int *);
+
+int __pthread_join(pthread_t t, void **res)
+{
+	int tmp, cs;
+	__pthread_testcancel();
+	__pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs);
+	if (cs == PTHREAD_CANCEL_ENABLE) __pthread_setcancelstate(cs, 0);
+	while ((tmp = t->tid)) __timedwait_cp(&t->tid, tmp, 0, 0, 0);
+	__pthread_setcancelstate(cs, 0);
+	a_barrier();
+	if (res) *res = t->result;
+	if (t->map_base) __munmap(t->map_base, t->map_size);
+	return 0;
+}
+
+weak_alias(__pthread_join, pthread_join);