[libcxx] [test] Unbreak passing multiple env variables in ssh.py

[mstorsjo]

Summary

No test actually does this, but this makes the option behave like
the corresponding one in run.py.

This was broken by commit b8b23aa80eefe84187d6ba364d06496c90c53bdb
(https://reviews.llvm.org/D99242) which introduced quoting; instead
of quoting the whole space separated list, quote each individual
argument.

libcxx/utils/ssh.py

try:
 
         # Execute the command through SSH in the temporary directory, with the
         # correct environment. We tweak the command line to run it on the remote
         # host by transforming the path of test-executables to their path in the
         # temporary directory on the remote host.
         commandLine = (pathOnRemote(x) if isTestExe(x) else x for x in commandLine)
         remoteCommands.append('cd {}'.format(tmp))
         if args.env:
-            remoteCommands.append('export {}'.format(cmd_quote(' '.join(args.env))))
+            env = list(map(cmd_quote, args.env))
+            remoteCommands.append('export {}'.format(' '.join(args.env)))
         remoteCommands.append(subprocess.list2cmdline(commandLine))
 
         # Finally, SSH to the remote host and execute all the commands.
         rc = subprocess.call(ssh(args, ' && '.join(remoteCommands)))
         return rc
 
     finally:
         # Make sure the temporary directory is removed when we're done.
         subprocess.check_call(ssh(args, 'rm -r {}'.format(tmp)))
 
 
 if __name__ == '__main__':
     exit(main())