[llvm] [lit] Fix to make "RUN: env PATH=..." work as intended (PR #165308)

[Alexander Richardson via llvm-commits]

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@@ -0,0 +1,4 @@
+#!/bin/sh
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arichardson wrote:

> I thought about using python, but couldn't find a good way to make it work. The only executable that is in PATH is test.py itself, so python isn't in the PATH. That is why I though /bin/sh could be assumed to always exist in supported linux installations.

Ah yes that is awkward, we'd have to generate a script with `#!{sys.executable}` but that might not work on windows. So probably best to keep as-is

https://github.com/llvm/llvm-project/pull/165308