Hi @Jordi_Suazo ,
and welcome to the ROOT forum! Why are you building ROOT from source? You can install ROOT on Ubuntu 20.04 with package managers or downloading a pre-compiled binary, see https://root.cern/install .
I don’t think I have ever seen those particular xrootd errors, but if you can install xrootd as a system package then ROOT won’t try (and somehow fail) to build xrootd as part of its build.