Make gensyscalls.py use the ALIAS_SYMBOL macro.

Change-Id: Ib94c0abb6fc85126ecc5ed3f1962b2b8b90b9952
diff --git a/libc/arch-arm64/syscalls/sendfile.S b/libc/arch-arm64/syscalls/sendfile.S
index 17a0d46..50ac12d 100644
--- a/libc/arch-arm64/syscalls/sendfile.S
+++ b/libc/arch-arm64/syscalls/sendfile.S
@@ -13,5 +13,4 @@
     ret
 END(sendfile)
 
-    .globl sendfile64
-    .equ sendfile64, sendfile
+ALIAS_SYMBOL(sendfile64, sendfile)