Issue title: Installer will create a folder named `~` under home directory
 Issue body: ## Expected behavior, english is recommend
A directory named `~` will be created under home directory during installation.

## Environment Information
- OS: Mac OS X
- vim version:
- neovim version: 0.17

## The reproduce ways from Vim starting (Required!)
```
curl -sLf https://spacevim.org/install.sh | bash
```

## Output of the ":message" command, and ":echo SpaceVim#logger#viewLog()"
A directory named `~` will be created under home directory.  The content of this directory looks like:
```
~/~/.cache/vimfilesrepos/github.com/Shougo/dein.vim
```

please post log below, if you want me reproduce your issue quickly, post your custom config here will be better.


 Comments: 
 Comment 0: oh, it is a bug, will check it tonight.
 Comment 1: @cjppku I can not reproduce it , what is your custom conifg, and 
what is the result of 
`:echo g:spacevim_plugin_bundle_dir`
 Comment 2: i had met the same bug ,but i haven't take it in my heart ago.
 Comment 3: but I can not reproduce it, does it happend with default config?
 Comment 4: yes,probably the default config,my home dir also have the ~ directory 
 Comment 5: do you me `/home/root/~/`?
 Comment 6: /home/leon/~ 






 Comment 7: can you delete it, and with default config, will this dir be created again?
 Comment 8: it disapperead
 Comment 9: I think it should be fixed in master. 
{'source': 'GithubIssues', 'repo_name_with_owner': 'SpaceVim/SpaceVim', 'issue_id': 214574707, 'repo_stars': 21073.0}