Revert "Add bullet thirdparty library"

This reverts commit f1d5672818.

core/CMakeLists.txt

@@ -5,6 +5,9 @@ find_package(OpenGL REQUIRED)
 find_package(GLEW REQUIRED)
 find_package(glfw3 3.3 REQUIRED)
 
+## Find Bullet
+find_package(Bullet REQUIRED)
+
 if (LUA_ENABLED)
 ## Find Lua
 find_package(Lua REQUIRED)
@@ -78,12 +81,17 @@ target_include_directories(couchlib
   PUBLIC
   ${CMAKE_CURRENT_SOURCE_DIR})
 
+target_include_directories(couchlib
+  PUBLIC
+  ${BULLET_INCLUDE_DIRS})
+
 target_link_libraries(couchlib glfw)
 target_link_libraries(couchlib OpenGL::GL)
 target_link_libraries(couchlib GLEW::GLEW)
 if (LUA_ENABLED)
   target_link_libraries(couchlib_luascripting ${LUA_LIBRARIES})
 endif () 
+target_link_libraries(couchlib ${BULLET_LIBRARIES})
 
 ## Add documentation
 find_package(Doxygen REQUIRED