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

fusl/src/thread/aarch64/syscall_cp.s

Index: fusl/src/thread/aarch64/syscall_cp.s
diff --git a/fusl/src/thread/aarch64/syscall_cp.s b/fusl/src/thread/aarch64/syscall_cp.s
new file mode 100644
index 0000000000000000000000000000000000000000..41db68af9588a02f524fdd971ccb1737e5031a68
--- /dev/null
+++ b/fusl/src/thread/aarch64/syscall_cp.s
@@ -0,0 +1,32 @@
+// __syscall_cp_asm(&self->cancel, nr, u, v, w, x, y, z)
+//                  x0             x1  x2 x3 x4 x5 x6 x7
+
+// syscall(nr, u, v, w, x, y, z)
+//         x8  x0 x1 x2 x3 x4 x5
+
+.global __cp_begin
+.hidden __cp_begin
+.global __cp_end
+.hidden __cp_end
+.global __cp_cancel
+.hidden __cp_cancel
+.hidden __cancel
+.global __syscall_cp_asm
+.hidden __syscall_cp_asm
+.type __syscall_cp_asm,%function
+__syscall_cp_asm:
+__cp_begin:
+	ldr w0,[x0]
+	cbnz w0,__cp_cancel
+	mov x8,x1
+	mov x0,x2
+	mov x1,x3
+	mov x2,x4
+	mov x3,x5
+	mov x4,x6
+	mov x5,x7
+	svc 0
+__cp_end:
+	ret
+__cp_cancel:
+	b __cancel