[CodeGen] Add target triple to test (NFC)

Exact IR may depend on target.

Author: nikic

clang/test/CodeGen/clear_cache.c

@@ -1,5 +1,5 @@
 // NOTE: Assertions have been autogenerated by utils/update_cc_test_checks.py
-// RUN: %clang_cc1 -emit-llvm %s -o - | FileCheck %s
+// RUN: %clang_cc1 -triple x86_64-linux-gnu -emit-llvm %s -o - | FileCheck %s
 
 char buffer[32] = "This is a largely unused buffer";