fix: add autogenerated build files to .gitignore

[halamix2]

Linux compilation creates some files that were not covered by the gitignore:

../game/mod_hl2mp_linux64
../game/mod_tf_linux64
.ninja_deps
.ninja_log
compile_commands.json
lib/public/linux64/mathlib.a
lib/public/linux64/raytrace.a
lib/public/linux64/tier1.a
lib/public/linux64/vgui_controls.a