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

fusl/src/thread/pthread_getattr_np.c

Index: fusl/src/thread/pthread_getattr_np.c
diff --git a/fusl/src/thread/pthread_getattr_np.c b/fusl/src/thread/pthread_getattr_np.c
new file mode 100644
index 0000000000000000000000000000000000000000..10ea512733fad390ac5cc699438cf1e4c02f06a2
--- /dev/null
+++ b/fusl/src/thread/pthread_getattr_np.c
@@ -0,0 +1,23 @@
+#define _GNU_SOURCE
+#include "pthread_impl.h"
+#include "libc.h"
+#include <sys/mman.h>
+
+int pthread_getattr_np(pthread_t t, pthread_attr_t *a)
+{
+	*a = (pthread_attr_t){0};
+	a->_a_detach = !!t->detached;
+	if (t->stack) {
+		a->_a_stackaddr = (uintptr_t)t->stack;
+		a->_a_stacksize = t->stack_size - DEFAULT_STACK_SIZE;
+	} else {
+		char *p = (void *)libc.auxv;
+		size_t l = PAGE_SIZE;
+		p += -(uintptr_t)p & PAGE_SIZE-1;
+		a->_a_stackaddr = (uintptr_t)p;
+		while (mremap(p-l-PAGE_SIZE, PAGE_SIZE, 2*PAGE_SIZE, 0)==MAP_FAILED && errno==ENOMEM)
+			l += PAGE_SIZE;
+		a->_a_stacksize = l - DEFAULT_STACK_SIZE;
+	}
+	return 0;
+}