cmake: sync gamemode conditionals with code after 5eec980a

FAILED: bin/yuzu
ld: error: unable to find library -lgamemode

FAILED: bin/yuzu-cmd
ld: error: undefined symbol: Common::Linux::StartGamemode()
>>> referenced by yuzu.cpp
>>>               src/yuzu_cmd/CMakeFiles/yuzu-cmd.dir/yuzu.cpp.o:(main)

ld: error: undefined symbol: Common::Linux::StopGamemode()
>>> referenced by yuzu.cpp
>>>               src/yuzu_cmd/CMakeFiles/yuzu-cmd.dir/yuzu.cpp.o:(main)