CMAKE_INSTALL_INCLUDEDIR was used before including GNUInstallDirs, causing the first configuration to miss INTERFACE_INCLUDE_DIRECTORIES. Configuring a second time worked, though. Tested with CMake 3.17.5.
I haven't included it here, as I think it might be a breaking change for existing users, but I'd also suggest changing the name of the configuration file from Config.cmake to v8pp-config.cmake or v8ppConfig.cmake, as currently it looks like the config filename needs to be included in the find(). e.g. find_package(v8pp REQUIRED CONFIGS Config.cmake)
CMAKE_INSTALL_INCLUDEDIR was used before including GNUInstallDirs, causing the first configuration to miss INTERFACE_INCLUDE_DIRECTORIES. Configuring a second time worked, though. Tested with CMake 3.17.5.
I haven't included it here, as I think it might be a breaking change for existing users, but I'd also suggest changing the name of the configuration file from Config.cmake to v8pp-config.cmake or v8ppConfig.cmake, as currently it looks like the config filename needs to be included in the find(). e.g. find_package(v8pp REQUIRED CONFIGS Config.cmake)
For the supported filenames, see the "Config mode" section in https://cmake.org/cmake/help/latest/command/find_package.html#search-modes