Directory names with -I prefix provided in target_include_directories call for dictionary target. As result, CXX flags for dictionary compilation include wrong directory names.
Example is in build directory file: `io/io/CMakeFiles/G__RIO.dir/flags.make`
CXX_INCLUDES = -I/home/linev/git/root/io/io/-I/home/linev/git/root -I/home/linev/git/root/io/io/-I/home/linev/build/root/etc/cling ...
Possible bugfix is: https://github.com/root-project/root/pull/5172
Same fix integrated in: https://github.com/root-project/root/pull/5181
While #5181 is only dedicated for master, #5172 can be applied for v6.18 and v6.20