fixed build system

docs/CMakeLists.txt

@@ -3,14 +3,14 @@
 #
 
 set(DOXY_SOURCE_DIRECTORY ${entt_SOURCE_DIR}/src)
-set(DOXY_DOCS_DIRECTORY ${entt_SOURCE_DIR}/docs)
-set(DOXY_OUTPUT_DIRECTORY ${entt_BINARY_DIR})
+set(DOXY_DOCS_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR})
+set(DOXY_OUTPUT_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR})
 
-configure_file(doxy.in ${entt_BINARY_DIR}/doxy.cfg @ONLY)
+configure_file(doxy.in doxy.cfg @ONLY)
 
 add_custom_target(
     docs ALL
-    COMMAND ${DOXYGEN_EXECUTABLE} ${entt_BINARY_DIR}/doxy.cfg
+    COMMAND ${DOXYGEN_EXECUTABLE} ${CMAKE_CURRENT_BINARY_DIR}/doxy.cfg
     WORKING_DIRECTORY ${entt_SOURCE_DIR}
     VERBATIM
     SOURCES doxy.in