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

fusl/src/thread/vmlock.c

Index: fusl/src/thread/vmlock.c
diff --git a/fusl/src/thread/vmlock.c b/fusl/src/thread/vmlock.c
new file mode 100644
index 0000000000000000000000000000000000000000..75f3cb76190fe4e8796997e7c3d29af80fb36792
--- /dev/null
+++ b/fusl/src/thread/vmlock.c
@@ -0,0 +1,21 @@
+#include "pthread_impl.h"
+
+static volatile int vmlock[2];
+
+void __vm_wait()
+{
+	int tmp;
+	while ((tmp=vmlock[0]))
+		__wait(vmlock, vmlock+1, tmp, 1);
+}
+
+void __vm_lock()
+{
+	a_inc(vmlock);
+}
+
+void __vm_unlock()
+{
+	if (a_fetch_add(vmlock, -1)==1 && vmlock[1])
+		__wake(vmlock, -1, 1);
+}