GN: Fix Visual Studio project build command

The previous solution didn't work for building projects with
non-default toolchains.
Now it calls ninja with the dependency output of a target
instead of the project name, this seems to work in all cases.

R=brettw@chromium.org, tmoniuszko@opera.com
BUG=

Review URL: https://codereview.chromium.org/1723663006

Cr-Original-Commit-Position: refs/heads/master@{#377277}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: d8d1d8e78b428862455838efef25593c0f69a46a
2 files changed
tree: da93a0f2544ade3931d424be62128f122d8b40e4
  1. tools/