Make gensyscalls.py use the ALIAS_SYMBOL macro.

Change-Id: Ib94c0abb6fc85126ecc5ed3f1962b2b8b90b9952
diff --git a/libc/arch-x86/syscalls/fstatat64.S b/libc/arch-x86/syscalls/fstatat64.S
index a3697e6..90e87b6 100644
--- a/libc/arch-x86/syscalls/fstatat64.S
+++ b/libc/arch-x86/syscalls/fstatat64.S
@@ -35,5 +35,4 @@
     ret
 END(fstatat64)
 
-    .globl fstatat
-    .equ fstatat, fstatat64
+ALIAS_SYMBOL(fstatat, fstatat64)