Make gensyscalls.py use the ALIAS_SYMBOL macro.

Change-Id: Ib94c0abb6fc85126ecc5ed3f1962b2b8b90b9952
diff --git a/libc/arch-arm64/syscalls/truncate.S b/libc/arch-arm64/syscalls/truncate.S
index 0e5a33e..e01cc7d 100644
--- a/libc/arch-arm64/syscalls/truncate.S
+++ b/libc/arch-arm64/syscalls/truncate.S
@@ -13,5 +13,4 @@
     ret
 END(truncate)
 
-    .globl truncate64
-    .equ truncate64, truncate
+ALIAS_SYMBOL(truncate64, truncate)