Handle ports without copyright file

[traversaro]

Some vcpkg ports to do not have copyright files:

CMake Error: File C:/vcpkg/packages/atlmfc_x64-windows/share/atlmfc/copyright does not exist.
CMake Error at CMakeLists.txt:297 (configure_file):
  configure_file Problem configuring file


CMake Error: File C:/vcpkg/packages/boost-modular-build-helper_x64-windows/share/boost-modular-build-helper/copyright does not exist.
CMake Error at CMakeLists.txt:297 (configure_file):
  configure_file Problem configuring file


CMake Error: File C:/vcpkg/packages/boost-vcpkg-helpers_x64-windows/share/boost-vcpkg-helpers/copyright does not exist.
CMake Error at CMakeLists.txt:297 (configure_file):
  configure_file Problem configuring file

typically this is for small ports that do not use external files, but are self-contained in vcpkg. For this reason, I think that using the vcpkg LICENSE for this ports make sense.

[drdanz]

🤔 I thought the copyright file was mandatory in vcpkg...

[traversaro]

I guess it is not for ports that do not get files from outside vcpkg, you can just assume the vcpkg license.