GN: Allow setting the path to Python

This allows setting the path to Python executable used by GN through
a command line argument so that it can be overriden by the user.

Review-Url: https://codereview.chromium.org/1978693002
Cr-Original-Commit-Position: refs/heads/master@{#393683}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 325472663a3576438dd275b2981d59764ea362fb
5 files changed
tree: 8352a2f486299f2a59b59d14779f700715885710
  1. tools/