message: Fixed incorrect VS 2015 detection
  The default algorithm for detecting VS 2015 installations searches for a missing "vcvarsall.bat" in the "VS140COMNTOOLS" path.
  So for detecting older versions of VS we also can use the new detection routine by using "vswhere" with the "-legacy" option.
diff: @@ -305,7 +305,7 @@ const ENVIRONMENTS: EnvironmentProvider[] = [
  log.verbose('VSWhere is not installed. Not searching for VS 2017');
  return [];
  }
  - const vswhere_res = await async.execute(vswhere, ['-all', '-format', 'json', '-products', '*']);
  + const vswhere_res = await async.execute(vswhere, ['-all', '-format', 'json', '-products', '*', '-legacy']);
  const installs: VSWhereItem[] = JSON.parse(vswhere_res.stdout);
  const archs = ['x86', 'amd64', 'arm'];
  const all_promices = installs
  