Fix missing variable MSVS expansion of copies arguments with Ninja.

The Visual Studio emulation does not expand the special
variables like 'VSInstallDir' into the 'copies' actions.

Here is a small broken example:

{
  'targets': [
    {
      'target_name': 'Copy_Target',
      'type': 'none',
      'copies': [
        {
          'destination': '<(PRODUCT_DIR)',
          'files': [
            '$(VSInstallDir)\\bin\\cl.exe',
          ],
        },
      ],
    },
  ],
}

Patch from etienneb@chromium.org.

R=scottmg@chromium.org

Review URL: https://codereview.chromium.org/194883010

git-svn-id: http://gyp.googlecode.com/svn/trunk@1870 78cadc50-ecff-11dd-a971-7dbc132099af
3 files changed