Skip making html documenttaion even if Doxygen is installed

Index: docs/CMakeLists.txt
--- docs/CMakeLists.txt.orig
+++ docs/CMakeLists.txt
@@ -32,7 +32,7 @@ foreach(file IN LISTS source_files)
 endforeach()
 
 set(DOXYGEN_SKIP_DOT TRUE)
-find_package(Doxygen)
+#find_package(Doxygen)
 
 if (NOT DOXYGEN_FOUND OR DOXYGEN_VERSION VERSION_LESS "1.9.8")
     message(STATUS "Documentation generation requires Doxygen 1.9.8 or later")
