ninja/win: Support VCLinkerTool.GenerateManifest

Currently Ninja generator always expects VCLinkerTool.GenerateManifest is true. With this CL, it will be configurable like MSVS generator.

BUG=gyp:389
TEST=python gyptest.py test/win/gyptest-link-generate-manifest.py
R=scottmg@chromium.org

Review URL: https://codereview.chromium.org/97873002

git-svn-id: http://gyp.googlecode.com/svn/trunk@1802 78cadc50-ecff-11dd-a971-7dbc132099af