Modify CMakeLists to use add_subdirectory where appropriate, instead of include.

CMakeLists.txt

@@ -15,4 +15,4 @@ set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} "${CMAKE_SOURCE_DIR}/cmake/modules/")
 
 
 ## Include Panda3D Packages ##
-include(${CMAKE_SOURCE_DIR}/dtool/Package.cmake)
+add_subdirectory(dtool)

dtool/CMakeLists.txt

@@ -35,11 +35,11 @@ set(DTOOL_INSTALL "${INSTALL_DIR}" CACHE STRING "The directory in which to insta
 
 set(DEFAULT_PRC_DIR "${INSTALL_DIR}/etc" CACHE STRING "Panda uses prc files for runtime configuration. Panda will search the default .prc directory if the PRC_PATH and PRC_DIR environment variables are not defined.")
 
+include(${CMAKE_CURRENT_LIST_DIR}/Configure.cmake)
 
 ## Include dtool subpackages ##
-include(${CMAKE_CURRENT_LIST_DIR}/Configure.cmake)
-include(${CMAKE_CURRENT_LIST_DIR}/src/dtoolbase/Sources.cmake)
-include(${CMAKE_CURRENT_LIST_DIR}/src/dtoolutil/Sources.cmake)
+add_subdirectory(src/dtoolbase)
+add_subdirectory(src/dtoolutil)
 
 ## Include dtool metalibs ##
-include(${CMAKE_CURRENT_LIST_DIR}/metalibs/dtool/Sources.cmake)
+add_subdirectory(metalibs/dtool)