GN: Improve bootstrap for Windows

Improve bootstrap for Windows and allow bootstrap to work in specified
target directory. Additionally, some fixes made to project generation,
and for Linux.

R=dpranke@chromium.org

Change-Id: Ied7f99d3cb83559fbde597cb707b46fcb3e98dc4
Reviewed-on: https://chromium-review.googlesource.com/941214
Commit-Queue: Yngve Pettersen <yngve@vivaldi.com>
Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#547867}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 73b7854e6d4c7a186047809aacb9ce1478277c7a
1 file changed