A few places in configure were doing ad-hoc calls to
the symlink function to set up symlinks from the build tree
back to the source tree. We have a loop that does this
already for all files and directories listed in the LINKS
environment variable; use that instead.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>