Make specifying C++ flags to be used by all linters possible

In my nvim settings I have the following lines:

```
let g:ale_cpp_cc_options = '-std=c++17 -Wall'
let g:ale_cpp_clang_options = '-std=c++17 -Wall'
let g:ale_cpp_clangd_options = '-std=c++17 -Wall'
let g:ale_cpp_clangcheck_options = '--extra-arg=-std=c++17 --extra-arg=-Wall'
let g:ale_cpp_clangtidy_options = '-std=c++17 -Wall'
let g:ale_cpp_gcc_options = '-std=c++17 -Wall'
```

It would be nice if it would be possible to specify C++ options, that would be used for every linter, so that you wouldn't need to repeat the options for each. Something like
```
let g:ale_cpp_flags = `-std=c++17 -Wall`
```
or
```
let g:ale_cpp_std=`c++17`
let g:ale_cpp_flags=`-Wall`
```