[libc++] Capture the current environment in the new test format

[broadwaylamb]

Summary

In the old test format we set the test execution environment to the current process environment (see https://github.com/llvm/llvm-project/blob/9e1455dc236252a60066c312c6d2e8a7ed66f609/libcxx/utils/libcxx/test/format.py#L179) for .sh.cpp tests.

In the new test format, where all tests are essentially ShTests, we should do the same. Otherwise executing tests over SSH may not work, at least on Windows hosts. For example, for me all SSH commands ended up exiting with code 255 without any error messages. After this change they succeed.

[ldionne]

libcxx/utils/libcxx/test/newformat.py

243

Yup, so I've been having to add the same workaround locally in some cases for ssh-agent environment variables to be picked up. However, I'm not certain this is the right place to set that, I think it should be in config.py instead.

[ldionne]

As discussed offline, done as 267273563dd974abe1d7cda4513fef884cf0eb3e.

libcxx/utils/libcxx/test/newformat.py

def _executeShTest(self, test, litConfig, steps, fileDependencies=None):
         testDir = os.path.dirname(test.getSourcePath())
         fileDependencies = [f if os.path.isabs(f) else os.path.join(testDir, f) for f in fileDependencies]
         substitutions.append(('%{file_dependencies}', ' '.join(map(pipes.quote, fileDependencies))))
 
         # Perform substitution in the script itself.
         script = lit.TestRunner.applySubstitutions(script, substitutions,
                                                    recursion_limit=recursiveExpansionLimit)
 
+        test.config.environment = dict(os.environ)
+
         return lit.TestRunner._runShTest(test, litConfig, useExternalSh, script, tmpBase)