[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'
-config.test_format = lit.formats.ShTest(execute_external)
+#
+# We prefer the lit internal shell which provides a better user experience on failures
+# unless the user explicitly disables it with LIT_USE_INTERNAL_SHELL=0 env var.
+use_lit_shell = True
+lit_shell_env = os.environ.get("LIT_USE_INTERNAL_SHELL")
+if lit_shell_env:
+  use_lit_shell = not lit.util.pythonize_bool(lit_shell_env)
+
+config.test_format = lit.formats.ShTest(execute_external=not use_lit_shell)
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rnk wrote:

If there are no uses of REQUIRES: shell in Polly, then I suppose it's not worth tracking the feature.

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