[polly] [polly][llvm-lit] Enabled lit internal shell for polly test suite (PR #105704)

[Reid Kleckner via llvm-commits]

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@@ -16,8 +16,15 @@ config.name = 'Polly - isl unit tests'
 #
 # For now we require '&&' between commands, until they get globally killed and
 # the test runner updated.
-execute_external = platform.system() != 'Windows'
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rnk wrote:

@petrhosek this is the copy-pasted Windows logic I was talking about. To my knowledge, every major LLVM lit test suite copies this logic, so in practice, everyone uses the internal shell on Windows.

https://github.com/llvm/llvm-project/pull/105704