[llvm] [llvm-lit][NVPTX] Use the shell's `ptxas` if `LLVM_PTXAS_EXECUTABLE` isn't set (PR #132810)

[Justin Fargnoli via llvm-commits]

https://github.com/justinfargnoli created https://github.com/llvm/llvm-project/pull/132810

None

>From ad13f699d110761e3ad861eb7b9e43c7e0c9b3c6 Mon Sep 17 00:00:00 2001
From: Justin Fargnoli <jfargnoli at nvidia.com>
Date: Fri, 21 Mar 2025 21:37:12 +0000
Subject: [PATCH] [llvm-lit] Use the shell's `ptxas` if `LLVM_PTXAS_EXECUTABLE`
 isn't set

---
 llvm/test/lit.cfg.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/llvm/test/lit.cfg.py b/llvm/test/lit.cfg.py
index aad7a088551b2..de2bddfdd07c5 100644
--- a/llvm/test/lit.cfg.py
+++ b/llvm/test/lit.cfg.py
@@ -6,6 +6,7 @@
 import sys
 import re
 import platform
+import shutil
 import subprocess
 
 import lit.util
@@ -345,7 +346,7 @@ def version_int(ver):
 
 
 ptxas_executable = (
-    os.environ.get("LLVM_PTXAS_EXECUTABLE", None) or config.ptxas_executable
+    os.environ.get("LLVM_PTXAS_EXECUTABLE", None) or config.ptxas_executable or shutil.which("ptxas")
 )
 if ptxas_executable:
     enable_ptxas(ptxas_executable)