[SystemZ][z/OS] don't write to source

test invoked clang that has tried to write in source directory that
might be readonly #111053

for 4c26a1e

Author: metaflow

clang/test/SemaCXX/pragma-pack-packed-2.cpp

@@ -1,6 +1,6 @@
 // RUN: %clang_cc1 -triple s390x-ibm-zos -fzos-extensions -fsyntax-only -verify %s
 // RUN: %clang_cc1 -triple s390x-ibm-zos -fzos-extensions -fxl-pragma-pack -fsyntax-only -verify %s
-// RUN: %clang -target s390x-ibm-zos -S -emit-llvm -Xclang -verify -fno-xl-pragma-pack %s
+// RUN: %clang -target s390x-ibm-zos -S -emit-llvm -Xclang -verify -fno-xl-pragma-pack -o %t.ll %s
 
 #pragma pack(show) // expected-warning {{value of #pragma pack(show) == 8}}
 #pragma pack(twobyte)