BTags not returning any results with universal-ctags on Termux

- [x] I have fzf 0.30.0 or above
- [x] I have read through https://github.com/junegunn/fzf.vim/blob/master/README.md
- [x] I have read through https://github.com/junegunn/fzf/blob/master/README-VIM.md
- [x] I have read through the manual page of fzf (`man fzf`)
- [x] I have searched through the existing issues

- Category
- [ ] Question
- [x] Bug
- [ ] Suggestion
- OS
- [ ] Linux
- [ ] macOS
- [ ] Windows
- [x] Termux/Android
- Vim
- [ ] Vim
- [x] NeoVim

note: Unfortunately I couldn't try vim's minimal configuration, since in my case my problem is only happening on my Android [Termux](https://play.google.com/store/apps/details?id=com.termux&hl=en&gl=US) application, and the vim minimal configuration example assumes that you are a root user (I'll have to root my android to do that) - The script itself writes stuff to the `/tmp` directory, which can only be done by a root user on Android.

That said I've done a lot of [homework](https://vi.stackexchange.com/questions/36851/how-to-view-the-full-shell-error-from-a-vim-script) before I made this post.

My problem is very similar to the one posted [here](https://github.com/junegunn/fzf.vim/issues/671), however I made sure that it's not a temporary directory problem, I put this in my `~/.config/nvim/init.vim`

```
if empty($TMPDIR)
let $TMPDIR = '/data/data/com.termux/files/usr/tmp'
endif
```

and I still got the same problem.

# Problem
When I run `:BTags` on a file, no tags show up, specifically I get [this](https://github.com/junegunn/fzf.vim/blob/master/autoload/fzf/vim.vim#L832) error

```
No tags found
```
I debugged the exact command that runs, and it works fine when I run it on the terminal like so

```
ctags -f - --sort=yes --excmd=number 'app/Repositories/Orders/AppOrdersRepo.php' 2> /dev/null | sort -s -k 5

App\\Http\\Controllers\\Orders app/Http/Controllers/Orders/CheckoutController.php 3;" n
checkout app/Http/Controllers/Orders/CheckoutController.php 69;" f
..
```

What am I missing?