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

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-backend-nvptx

Author: Justin Fargnoli (justinfargnoli)

<details>
<summary>Changes</summary>



---
Full diff: https://github.com/llvm/llvm-project/pull/132810.diff


1 Files Affected:

- (modified) llvm/test/lit.cfg.py (+2-1) 


``````````diff
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)

``````````

</details>


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