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

fusl/src/thread/pthread_condattr_setpshared.c

Index: fusl/src/thread/pthread_condattr_setpshared.c
diff --git a/fusl/src/thread/pthread_condattr_setpshared.c b/fusl/src/thread/pthread_condattr_setpshared.c
new file mode 100644
index 0000000000000000000000000000000000000000..51453e0480a822aa88f3797c586d6ceb2e4bb7b3
--- /dev/null
+++ b/fusl/src/thread/pthread_condattr_setpshared.c
@@ -0,0 +1,9 @@
+#include "pthread_impl.h"
+
+int pthread_condattr_setpshared(pthread_condattr_t *a, int pshared)
+{
+	if (pshared > 1U) return EINVAL;
+	a->__attr &= 0x7fffffff;
+	a->__attr |= (unsigned)pshared<<31;
+	return 0;
+}