Escape rustfmt config path

Author: b8591340

autoload/rustfmt.vim

@@ -63,12 +63,12 @@ endfunction
 function! s:RustfmtConfigOptions()
     let l:rustfmt_toml = findfile('rustfmt.toml', expand('%:p:h') . ';')
     if l:rustfmt_toml !=# ''
-        return '--config-path '.fnamemodify(l:rustfmt_toml, ":p")
+        return '--config-path '.shellescape(fnamemodify(l:rustfmt_toml, ":p"))
     endif
 
     let l:_rustfmt_toml = findfile('.rustfmt.toml', expand('%:p:h') . ';')
     if l:_rustfmt_toml !=# ''
-        return '--config-path '.fnamemodify(l:_rustfmt_toml, ":p")
+        return '--config-path '.shellescape(fnamemodify(l:_rustfmt_toml, ":p"))
     endif
 
     " Default to edition 2018 in case no rustfmt.toml was found.