emulators/yuzu: unbreak build after 455717ffde60
CMake Warning at CMakeLists.txt:313 (find_package):
Could not find a configuration file for package "xbyak" that is compatible with requested version "6". The following configuration files were considered but not accepted: /usr/local/lib/cmake/xbyak/xbyak-config.cmake, version: 7.0
CMake Error at externals/CMakeLists.txt:19 (add_subdirectory):
The source directory externals/xbyak does not contain a CMakeLists.txt file.