This fixes the youcompleteme config script to look for ninja_output.py
in tools/vim instead of tools/ninja (it was moved there in
https://crrev.com/c/2797536), and makes a minor adjustment for python3
compatibility.

R=machenbach@chromium.org

Bug: v8:11879
Change-Id: Ia825903fb6019865244c5529bf2d23935a10ad5e
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3059077Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Reviewed-by: Zhi An Ng <zhin@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#75984}