Make gensyscalls.py use the ALIAS_SYMBOL macro.

Change-Id: Ib94c0abb6fc85126ecc5ed3f1962b2b8b90b9952
diff --git a/libc/arch-x86_64/syscalls/fstat64.S b/libc/arch-x86_64/syscalls/fstat64.S
index de57668..a0d4fa1 100644
--- a/libc/arch-x86_64/syscalls/fstat64.S
+++ b/libc/arch-x86_64/syscalls/fstat64.S
@@ -14,5 +14,4 @@
     ret
 END(fstat64)
 
-    .globl fstat
-    .equ fstat, fstat64
+ALIAS_SYMBOL(fstat, fstat64)