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

fusl/src/thread/aarch64/clone.s

Index: fusl/src/thread/aarch64/clone.s
diff --git a/fusl/src/thread/aarch64/clone.s b/fusl/src/thread/aarch64/clone.s
new file mode 100644
index 0000000000000000000000000000000000000000..50af913ce696796216e9d6551f92c7ac3a82dd97
--- /dev/null
+++ b/fusl/src/thread/aarch64/clone.s
@@ -0,0 +1,29 @@
+// __clone(func, stack, flags, arg, ptid, tls, ctid)
+//         x0,   x1,    w2,    x3,  x4,   x5,  x6
+
+// syscall(SYS_clone, flags, stack, ptid, tls, ctid)
+//         x8,        x0,    x1,    x2,   x3,  x4
+
+.global __clone
+.type   __clone,%function
+__clone:
+	// align stack and save func,arg
+	and x1,x1,#-16
+	stp x0,x3,[x1,#-16]!
+
+	// syscall
+	uxtw x0,w2
+	mov x2,x4
+	mov x3,x5
+	mov x4,x6
+	mov x8,#220 // SYS_clone
+	svc #0
+
+	cbz x0,1f
+	// parent
+	ret
+	// child
+1:	ldp x1,x0,[sp],#16
+	blr x1
+	mov x8,#93 // SYS_exit
+	svc #0