clang/test/CodeGen/2008-01-25-ByValReadNone.c: Add explicit -triple x86_64-unknown-unknown.

It would emit @llvm.memcpy with "-triple x86_64-(mingw32|win32)" and had been failing since Nick's r185735.

  ; Function Attrs: nounwind
  declare void @llvm.memcpy.p0i8.p0i8.i64(i8* nocapture, i8* nocapture readonly, i64, i32, i1) #1

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@185796 91177308-0d34-0410-b5e6-96231b3b80d8

test/CodeGen/2008-01-25-ByValReadNone.c

-// RUN: %clang_cc1 -emit-llvm -o - %s | FileCheck %s
+// RUN: %clang_cc1 -triple x86_64-unknown-unknown -emit-llvm -o - %s | FileCheck %s
 
 // XFAIL: mips
 
+// It could hit in @llvm.memcpy with "-triple x86_64-(mingw32|win32)".
 // CHECK-NOT: readonly
 // CHECK-NOT: readnone