[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:

Would making this a python script allow it to work on windows and avoid the /bin/sh dependency? This should be testable in pre-commit ci so you wouldn't need a windows system. 

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