Fix: Adjust .gitignore to CMake build system.

.gitignore

@@ -1,48 +1,4 @@
-bin/*
-!bin/ai
-bin/ai/*
-!bin/ai/compat*.nut
-!bin/ai/regression
-!bin/data
-bin/baseset/*
-!bin/baseset/openttd.grf
-!bin/baseset/opntitle.dat
-!bin/baseset/orig_extra.grf
-!bin/baseset/orig_*.obg
-!bin/baseset/orig_*.obs
-!bin/baseset/no_sound.obs
-!bin/baseset/no_music.obm
-!bin/baseset/orig_*.obm
-!bin/game
-bin/game/*
-!bin/game/compat*.nut
-!bin/scripts
-bin/scripts/*
-!bin/scripts/*.example
-!bin/scripts/readme.txt
-
-bundle/*
-bundles/*
+/build
 docs/aidocs/*
 docs/gamedocs/*
 docs/source/*
-media/openttd.desktop
-media/openttd.desktop.install
-projects/.vs
-projects/Debug
-projects/Release
-projects/*.ncb
-projects/*.suo
-projects/*.sdf
-projects/*.opensdf
-projects/*.vcproj.*.user
-projects/*.vcxproj.user
-projects/*.VC.db
-projects/*.VC.opendb
-
-/Makefile*
-!/Makefile.msvc
-/config.*
-!/config.lib
-!*.in
-*.tmp