"start-local-buildbot-server --ews" fails to start: builtins.ModuleNo…

…tFoundError: No module named 'ews-build'

https://bugs.webkit.org/show_bug.cgi?id=269688

Reviewed by Carlos Alberto Lopez Perez.

After 267005@main changed master.cfg to use importlib to load
loadConfig, start-local-buildbot-server failed to start. The basename
of _server_wordir should be same with the basename of _configdir.

* Tools/CISupport/start-local-buildbot-server:
(BuildbotTestRunner._setup_server_workdir): Use the basename of
_configdir instead of the hard-coded directory name 'buildbot-server'
for the basename of _server_wordir.

Canonical link: https://commits.webkit.org/275008@main

Tools/CISupport/start-local-buildbot-server

@@ -240,7 +240,7 @@ class BuildbotTestRunner(object):
         return result
 
     def _setup_server_workdir(self):
-        self._server_wordir = os.path.join(self._base_workdir_temp, 'buildbot-server')
+        self._server_wordir = os.path.join(self._base_workdir_temp, os.path.basename(self._configdir))
         assert(not os.path.exists(self._server_wordir))
         self._server_log = os.path.join(self._server_wordir, 'server.log')
         self._server_ready_fd = os.path.join(self._server_wordir, '.server-is-ready')