[BOLT] Enable lit internal shell by default

This patch enables lit's internal shell by default now that all
REQUIRES: shell tests have been update to not require shell features not
available in lit and all unresolved tests have been fixed.

This should speed up test runtime by a bit and will give nicer error
messaging.

Fixes llvm#102701.

Reviewers:
aaupov, yota9, maksfb, paschalis-mpeis, yozhu, rafaelauler, ayermolo

Reviewed By: maksfb

Pull Request: llvm#156083

Author: boomanaiden154

bolt/test/lit.cfg.py

@@ -18,11 +18,22 @@
 # name: The name of this test suite.
 config.name = "BOLT"
 
+# TODO: Consolidate the logic for turning on the internal shell by default for all LLVM test suites.
+# See https://github.com/llvm/llvm-project/issues/106636 for more details.
+#
+# We prefer the lit internal shell which provides a better user experience on failures
+# and is faster 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 = lit.util.pythonize_bool(lit_shell_env)
+
 # testFormat: The test format to use to interpret tests.
 #
 # For now we require '&&' between commands, until they get globally killed and
 # the test runner updated.
-config.test_format = lit.formats.ShTest(not llvm_config.use_lit_shell)
+config.test_format = lit.formats.ShTest(execute_external=not use_lit_shell)
 
 # suffixes: A list of file extensions to treat as test files.
 config.suffixes = [