[lit, shtest-timeout] Always use an internal shell for the shtest-timeout to diagnose buildbot failures

[stella.stamenova]

Summary

Right now this test is failing on the builtbots on Windows but we have a very similar setup where the test passes. The test is meant to test that specifying a timeout works correctly by running an infnite loop and having it timeout - on the buildbot, the infinite loop doesn't actually execute. This change runs all of the tests in the set using an internal shell rather than an external shell. I expect this will make the test pass which means that either the way the external shell is invoked or the external shell setup on the buildbots is not correct. Regardless of whether the test passes with this change, we'll need to undo this change and have a real fix.

@gkistanova was able to get logs from the buildbot to rule out a number of theories as to why this test is failing, but they didn't have enough information to confirm exactly what the issue is. The purpose of this change is to narrow it down, but if someone has a local repro and can aid in debugging, that would make it much speedier (and less prone to making the bots fail).

[rnk]

Sounds good. I'm not very interested in testing the external shell on Windows. Everyone should be migrated over to the internal one if possible.

[delcypher]

@ stella.stamenova Thanks for taking a look at fixing. Provided that this change isn't permanent then this change is probably okay.

llvm/trunk/utils/lit/tests/Inputs/shtest-timeout/lit.cfg

 # -*- Python -*-
 import os
 import sys
 
 import lit.formats
 
 config.name = 'per_test_timeout'
 
 shellType = lit_config.params.get('external', '1')
 
 if shellType == '0':
     lit_config.note('Using internal shell')
     externalShell = False
 else:
     lit_config.note('Using external shell')
-    externalShell = True
+    externalShell = (not sys.platform in ['win32'])
+    if not externalShell:
+        lit_config.note('External shell requested, but using internal shell')
 
 configSetTimeout = lit_config.params.get('set_timeout', '0')
 
 if configSetTimeout != '0':
     # Try setting the max individual test time in the configuration
     lit_config.maxIndividualTestTime = int(configSetTimeout)
 
 config.test_format = lit.formats.ShTest(execute_external=externalShell)
 config.suffixes = ['.py']
 
 config.test_source_root = os.path.dirname(__file__)
 config.test_exec_root = config.test_source_root
 config.target_triple = '(unused)'
 src_root = os.path.join(config.test_source_root, '..')
 config.environment['PYTHONPATH'] = src_root
 config.substitutions.append(('%{python}', '"%s"' % (sys.executable)))