Linux binaries can be significantly shrinked

I noticed that size of Linux binaries currently is around 30 Mb or more unlike Windows binaries with 10 Mb or less. The Linux binaries can be significantly optimized if use `-DCMAKE_CXX_FLAGS_RELEASE="-s"` option (see https://github.com/lightvector/KataGo/pull/1127/changes#diff-5c3fa597431eda03ac3339ae6bf7f05e1a50d6fc7333679ec38e21b337cb6721R38).