[llvm] [AIX] [lit] Fix shtest-format.py to account for behaviour on AIX (PR #121426)

[Mark Danial via llvm-commits]

https://github.com/madanial0 created https://github.com/llvm/llvm-project/pull/121426

The changes from https://github.com/llvm/llvm-project/pull/121376 has broken the ppc64 aix bot: https://lab.llvm.org/buildbot/#/builders/64/builds/1835. Adjusted the testcase to account for `cat` behaviour on AIX prior to the changes

>From 6dcfebad1167a54fc4976a3987e407d051c6fb3d Mon Sep 17 00:00:00 2001
From: Mark Danial <mark.danial at ibm.com>
Date: Wed, 1 Jan 2025 02:11:11 -0500
Subject: [PATCH] Fix shtest-format.py to account for behaviour on AIX

---
 llvm/utils/lit/tests/shtest-format.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/llvm/utils/lit/tests/shtest-format.py b/llvm/utils/lit/tests/shtest-format.py
index d58973993b272a..fda3ef52e8043b 100644
--- a/llvm/utils/lit/tests/shtest-format.py
+++ b/llvm/utils/lit/tests/shtest-format.py
@@ -18,7 +18,7 @@
 # CHECK: Command Output (stderr):
 # CHECK-NEXT: --
 # CHECK-NOT: --
-# CHECK: cat{{(_64)?(\.exe)?}}: {{.*does-not-exist.*}}: No such file or directory
+# CHECK: cat{{(_64)?(\.exe)?}}: {{(cannot open does-not-exist|.*does-not-exist.*: No such file or directory)}}
 # CHECK: --
 
 # CHECK: FAIL: shtest-format :: external_shell/fail_with_bad_encoding.txt