Index: llvm/trunk/lib/Fuzzer/test/lit.cfg
===================================================================
--- llvm/trunk/lib/Fuzzer/test/lit.cfg
+++ llvm/trunk/lib/Fuzzer/test/lit.cfg
@@ -6,6 +6,23 @@
 config.suffixes = ['.test']
 config.test_source_root = os.path.dirname(__file__)
 
+# Choose between lit's internal shell pipeline runner and a real shell.  If
+# LIT_USE_INTERNAL_SHELL is in the environment, we use that as an override.
+use_lit_shell = os.environ.get("LIT_USE_INTERNAL_SHELL")
+if use_lit_shell:
+    # 0 is external, "" is default, and everything else is internal.
+    execute_external = (use_lit_shell == "0")
+else:
+    # Otherwise we default to internal on Windows and external elsewhere, as
+    # bash on Windows is usually very slow.
+    execute_external = (not sys.platform in ['win32'])
+
+# 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(execute_external)
+
 # Tweak PATH to include llvm tools dir and current exec dir.
 llvm_tools_dir = getattr(config, 'llvm_tools_dir', None)
 if (not llvm_tools_dir) or (not os.path.exists(llvm_tools_dir)):