PNaCl: Add NoAlias attributes in ExpandByVal and ExpandVarArgs passes

test/Transforms/NaCl/expand-varargs-attrs.ll

 ; RUN: opt < %s -expand-varargs -S | FileCheck %s
 
 declare i32 @varargs_func(i32 %arg, ...)
 
 
 ; Check that attributes such as "byval" are preserved on fixed arguments.
 
 %MyStruct = type { i64, i64 }
 
 define void @func_with_arg_attrs(%MyStruct* byval, ...) {
   ret void
 }
-; CHECK: define void @func_with_arg_attrs(%MyStruct* byval, i8* %varargs) {
+; CHECK: define void @func_with_arg_attrs(%MyStruct* byval, i8* noalias %varargs) {
 
 
 declare void @take_struct_arg(%MyStruct* byval %s, ...)
 
 define void @call_with_arg_attrs(%MyStruct* %s) {
   call void (%MyStruct*, ...)* @take_struct_arg(%MyStruct* byval %s)
   ret void
 }
 ; CHECK: define void @call_with_arg_attrs(%MyStruct* %s) {
 ; CHECK: call void %vararg_func(%MyStruct* byval %s, %vararg_call{{.*}} %vararg_buffer)
@@ skipping 39 matching lines @@
 ; reads space alloca'd by the caller.
 define i32 @tail_call() {
   %result = tail call i32 (i32, ...)* @varargs_func(i32 111, i64 222)
   ret i32 %result
 }
 ; CHECK: define i32 @tail_call() {
 ; CHECK: %result = call i32 %vararg_func(i32 111
 
 
 ; CHECK: attributes #1 = { readonly }