Made build impervious to temp dir privileges

File::Temp::tempdir will usually create a dir in a global location (eg /tmp), but if the current user lacks privs for that location it will fallback to providing a local dir.  In the latter case a relative path is returned and t/mojolicious/command.t fails.  You could argue that's a fault on the client machine (it is) but Mojolicious shouldn't care and the build needn't fail.  The existing logic at that line of the test is a bit strange, so adopting the change will
  * remove some unhelpful bytes from the test file
  * make the build not care about strange perms on the global temp dir
  * make Fridays slightly sunnier, with a pleasant aroma of warm chestnuts