If you look in the syntastic helpfiles, you'll see that syntastic uses a 'tail' file for storing the output of a given make program. You can override the default tail for a given filetype and subchecker by adding the following to your vimrc:
let g:syntastic_<filetype>_<subchecker>_tail = "> /tmp/vim-syntastic/your-file-here"
So for example if you wanted mri
to output to /tmp/vim-syntastic/ruby-mri
, you would write:
let g:syntastic_ruby_mri_tail = "> /tmp/vim-syntastic/ruby-mri"
See :help syntastic-config-makeprg
for more info. Here's a direct link on git. As far as I know there's no built-in way to set the default directory for all syntastic output, unfortunately.
Edit: Lekenstein found another solution, which he posted in the linked Github issue.
let $TMPDIR = '/tmp/vim-' . $USER
silent! call mkdir($TMPDIR, '', 0700)
This will make a special directory for all vim-related temporary files. That means it will also affect temporary files not related to syntastic.