Fix #257 in preparation for #427, standardise options with fallbacks, and make it so every value can be computed dynamically

ale_linters/nim/nimcheck.vim

@@ -1,7 +1,6 @@
 " Author: Baabelfish
 " Description: Typechecking for nim files
 
-
 function! ale_linters#nim#nimcheck#Handle(buffer, lines) abort
     let l:buffer_filename = fnamemodify(bufname(a:buffer), ':p:t')
     let l:pattern = '^\(.\+\.nim\)(\(\d\+\), \(\d\+\)) \(.\+\)'
@@ -52,7 +51,10 @@ endfunction
 
 
 function! ale_linters#nim#nimcheck#GetCommand(buffer) abort
-    return 'nim check --path:' . fnameescape(fnamemodify(bufname(a:buffer), ':p:h')) . ' --threads:on --verbosity:0 --colors:off --listFullPaths %t'
+    let l:directory = fnameescape(fnamemodify(bufname(a:buffer), ':p:h'))
+
+    return 'nim check --path:' . l:directory
+    \   . ' --threads:on --verbosity:0 --colors:off --listFullPaths %t'
 endfunction