Make gensyscalls.py use the ALIAS_SYMBOL macro.

Change-Id: Ib94c0abb6fc85126ecc5ed3f1962b2b8b90b9952
diff --git a/libc/arch-arm64/syscalls/ftruncate.S b/libc/arch-arm64/syscalls/ftruncate.S
index c6e99f5..c21e098 100644
--- a/libc/arch-arm64/syscalls/ftruncate.S
+++ b/libc/arch-arm64/syscalls/ftruncate.S
@@ -13,5 +13,4 @@
     ret
 END(ftruncate)
 
-    .globl ftruncate64
-    .equ ftruncate64, ftruncate
+ALIAS_SYMBOL(ftruncate64, ftruncate)