message: [VS2017] Extract function that detects the VS2015 instance, when no VS2017 is found
diff: @@ -94,6 +94,13 @@ namespace vcpkg::Environment
  return Strings::split(ec_data.output, "\n");
  }
  + static const fs::path& get_VS2015_installation_instance()
  + {
  + static const fs::path vs2015_cmntools = fs::path(System::wdupenv_str(L"VS140COMNTOOLS")).parent_path(); // TODO: Check why this requires parent_path() call
  + static const fs::path vs2015_path = vs2015_cmntools.parent_path().parent_path();
  + return vs2015_path;
  + }
  +
  static fs::path find_dumpbin_exe(const vcpkg_paths& paths)
  {
  const std::vector<std::string> vs2017_installation_instances = get_VS2017_installation_instances(paths);
  @@ -111,8 +118,7 @@ namespace vcpkg::Environment
  }
  // VS2015
  - const fs::path vs2015_cmntools = fs::path(System::wdupenv_str(L"VS140COMNTOOLS")).parent_path(); // TODO: Check why this requires parent_path() call
  - const fs::path vs2015_dumpbin_exe = vs2015_cmntools.parent_path().parent_path() / "VC" / "bin" / "dumpbin.exe";
  + const fs::path vs2015_dumpbin_exe = get_VS2015_installation_instance() / "VC" / "bin" / "dumpbin.exe";
  paths_examined.push_back(vs2015_dumpbin_exe);
  if (fs::exists(vs2015_dumpbin_exe))
  {
  