Retire unmaintained CMakeLists.txt.

I added the CMakeLists.txt 6 or 7 years ago so I could load the code
into Jetbrains Clion. I have moved to another editor years ago and the
cmake stuff is effectively unmaintained since then. We kept it around
in case that we'll do a MSVC port, but that's unlikely at this point.
Since bugreport and problems with the CMakeLists.txt keep coming up,
finally retire them. They can be resurrected from the git history if
we'll ever need them again.

Part of yquake2/yquake2#725.

CMakeLists.txt

@@ -1,73 +0,0 @@
-cmake_minimum_required(VERSION 3.0)
-
-# Enforce "Debug" as standard build type
-if(NOT CMAKE_BUILD_TYPE)
-	set(CMAKE_BUILD_TYPE "Debug" CACHE STRING "Choose the type of build, options are: Debug Release RelWithDebInfo MinSizeRel." FORCE)
-endif(NOT CMAKE_BUILD_TYPE)
-
-# CMake project configuration
-project(yquake2-ctf)
-
-# Enforce compiler flags (GCC / Clang compatible, yquake2
-# won't build with another compiler anyways)
-#  -Wall                -> More warnings
-#  -fno-strict-aliasing -> Quake 2 is far away from strict aliasing
-#  -fwrapv              -> Make signed integer overflows defined
-set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wall -fno-strict-aliasing -fwrapv")
-
-# Use -O2 as maximum optimization level. -O3 has it's problems with yquake2.
-string(REPLACE "-O3" "-O2" CMAKE_C_FLAGS_RELEASE "${CMAKE_C_FLAGS_RELEASE}")
-
-# Linker Flags
-if(${CMAKE_SYSTEM_NAME} MATCHES "Windows")
-	list(APPEND CtfLinkerFlags "-lm")
-else()
-	list(APPEND CtfLinkerFlags "-lm -rdynamic")
-endif()
-
-set(Ctf-Source
-	src/menu/menu.c
-	src/monster/move.c
-	src/player/client.c
-	src/player/hud.c
-	src/player/trail.c
-	src/player/view.c
-	src/player/weapon.c
-	src/shared/shared.c
-	src/g_ai.c
-	src/g_chase.c
-	src/g_cmds.c
-	src/g_combat.c
-	src/g_ctf.c
-	src/g_func.c
-	src/g_items.c
-	src/g_main.c
-	src/g_misc.c
-	src/g_monster.c
-	src/g_phys.c
-	src/g_save.c
-	src/g_spawn.c
-	src/g_svcmds.c
-	src/g_target.c
-	src/g_trigger.c
-	src/g_utils.c
-	src/g_weapon.c
-	)
-
-set(Ctf-Header
-	src/header/ctf.h
-	src/header/game.h
-	src/header/local.h
-	src/header/menu.h
-	src/header/shared.h
-	src/monster/player.h
-	)
-
-# Build the ctf dynamic library
-add_library(game SHARED ${Ctf-Source} ${Ctf-Header})
-set_target_properties(game PROPERTIES
-	PREFIX ""
-	LIBRARY_OUTPUT_DIRECTORY_DEBUG ${CMAKE_BINARY_DIR}/Debug
-	LIBRARY_OUTPUT_DIRECTORY_RELEASE ${CMAKE_BINARY_DIR}/Release
-)
-target_link_libraries(game ${CtfLinkerFlags})