[libpff] Shoud not be limited to Windows

Is your feature request related to a problem? Please describe.

Thank you for a great job with libpff port, including special CMakeFile.txt. Unfortunately it does not support Linux and MacOS currently:

$ vcpkg/vcpkg install libpff:x64-linux-dynamic
Computing installation plan...
libpff is only supported on 'windows & !(static & windows) & !uwp & !xbox', which does not match x64-linux-dynamic. This usually means that there are known build failures, or runtime problems, when building other platforms. To ignore this and attempt to build libpff anyway, rerun vcpkg with `--allow-unsupported`.

libpff itself works perfectly on Linux and MacOS machines. Please find the alternative port here:
https://github.com/docwire/docwire/tree/master/ports/libpff-unix
It works fine on x64-linux-dynamic, x64-osx-dynamic, arm64-osx-dynamic and x64-windows.
It uses different aproach so we did not open pull request but the issue to discuss the situation as we would like to add DocWire SDK to VCPKG repository as well in the future. That dependency blocks us a bit.

Best regards.

Proposed solution

CMake and port files should be fixed to support other platforms or official port should be moved to alternative way similar to overlay port in https://github.com/docwire/docwire.

Describe alternatives you've considered

Alternative overlay port is available at https://github.com/docwire/docwire

Additional context

No response