input_common: Add support for GameCube Adapter

This is a port of the initial GameCube adapter input support i added into yuzu emulator.
It requires the same setup as when it was first introduced in yuzu, requiring the Zadig driver be installed for the adapter to allow it to interface with libusb.

CMakeLists.txt

@@ -193,6 +193,17 @@ if (ENABLE_QT)
     endif()
 endif()
 
+# Ensure libusb is properly configured (based on dolphin libusb include)
+if(NOT APPLE)
+    include(FindPkgConfig)
+    find_package(LibUSB)
+endif()
+if (NOT LIBUSB_FOUND)
+    add_subdirectory(externals/libusb)
+    set(LIBUSB_INCLUDE_DIR "")
+    set(LIBUSB_LIBRARIES usb)
+endif()
+
 if (ENABLE_FFMPEG)
     if (CITRA_USE_BUNDLED_FFMPEG)
         if ((MSVC_VERSION GREATER_EQUAL 1910 AND MSVC_VERSION LESS 1930) AND ARCHITECTURE_x86_64)