[lit] Keep stdout/stderr when using GoogleTest

[lenary]

Summary

When debugging issues with GoogleTest sharding, it is very useful to see
the stdout/stderr from the whole shard as part of the test failure
output.

This change ensures that the stream output and error code is kept and
logged in the case of any failures.

[tmatheson]

LGTM

[ychen]

sounds good. Could you please add a test? Probably in llvm/utils/lit/tests/googletest-format.py.

[lenary]

@ychen it would have been nice to give me a heads up you were going to land your own implementation. Sorry I didn’t manage to add a unit test before I went on vacation.

[ychen]

In D123797#3472697, @lenary wrote:

@ychen it would have been nice to give me a heads up you were going to land your own implementation. Sorry I didn’t manage to add a unit test before I went on vacation.

Thanks for letting me know. Sorry I have to commit it earlier since several folks reported that the missing stdout/stderr is making CI failures harder to debug and I didn't hear from you for a while ...

llvm/utils/lit/lit/formats/googletest.py

def execute(self, test, litConfig):
 
         def get_shard_header(shard_env):
             shard_envs = '\n'.join([k + '=' + v for k, v in shard_env.items()])
             return f"Script(shard):\n--\n%s\n%s\n--\n" % (shard_envs, ' '.join(cmd))
 
         shard_header = get_shard_header(shard_env)
 
         try:
-            _, _, exitCode = lit.util.executeCommand(
+            out, err, exitCode = lit.util.executeCommand(
                 cmd, env=test.config.environment,
                 timeout=litConfig.maxIndividualTestTime)
-        except lit.util.ExecuteCommandTimeoutException:
-            return (lit.Test.TIMEOUT, f'{shard_header}Reached timeout of '
-                    f'{litConfig.maxIndividualTestTime} seconds')
+        except lit.util.ExecuteCommandTimeoutException as e:
+            stream_msg = f"\n{e.out}\n--\n{e.err}\n--\nexit: {e.exitCode}\n--\n"
+            return (lit.Test.TIMEOUT, f'{shard_header}{stream_msg}Reached '
+                    f'timeout of {litConfig.maxIndividualTestTime} seconds')
 
+        stream_msg = f"\n{out}\n--\n{err}\n--\nexit: {exitCode}\n--\n"
         if not os.path.exists(test.gtest_json_file):
             errmsg = f"shard JSON output does not exist: %s" % (
                 test.gtest_json_file)
-            return lit.Test.FAIL, shard_header + errmsg
+            return lit.Test.FAIL, shard_header + stream_msg + errmsg
 
         if exitCode == 0:
             return lit.Test.PASS, ''
 
         with open(test.gtest_json_file, encoding='utf-8') as f:
             jf = json.load(f)
 
             if use_shuffle:
                 shard_env['GTEST_RANDOM_SEED'] = str(jf['random_seed'])
-            output = get_shard_header(shard_env) + '\n'
+            output = get_shard_header(shard_env) + stream_msg + '\n'
 
             for testcase in jf['testsuites']:
                 for testinfo in testcase['testsuite']:
                     result = testinfo['result']
                     if result == 'SUPPRESSED' or result == 'SKIPPED':
                         continue
                     testname = testcase['name'] + '.' + testinfo['name']
                     header = f"Script:\n--\n%s --gtest_filter=%s\n--\n" % (